Advice please: Stumped on choosing pianos (new to Pianoteq)

It's a tough choice. If you want absolute bang for buck (the most models) I suggest the following:

The New York D is part of a pack with the Hamburg D. The vast majority of concert hall pianos are Steinway, so yes a no brainer, especially now it's a pack.
The Ant.Petrof was joined by the Mistral as a pack too. So if you buy the Petrol pack with the D pack that's four piano models for the price of two, but that's me forgetting you now get three packs with Standard.   

The Vintage Tines pack is three pianos, if you like the electrics?

Not forgetting you can download this entire collection for free:
https://www.modartt.com/kivir

So you get the Errard and Pleyel pianos which also benefit from seventh generation Pianoteq. So you would have six grand pianos straight away. The latter two with a more characterful, imperfect sound. The Pleyel perhaps closest to a large upright in character, before you pick up U4 (but you could also pick that up in the current sale along with your third piano).
The free pack also has the CP80 for a classic late 70s, early 80s sound.   So seven highly usable pianos for Jazz, Rock and pop, along with the fine historic piano models, which are more of a niche interest.
https://www.modartt.com/cp-80
Play the CP80 enough you'll probably hanker after the Rhodes sound too. So maybe get Vintage Tines with the Rhodes and Wurly models in a single pack?

However, you could find yourself drawn more to any of the other modern pianos,  and something that actually inspires you to play more is ultimately the best value, so your mileage will almost certainly vary. For instance the K isn't even based on any one single real world piano and sounds great.

Better advice is to just suggest you play with all the models and decide for yourself. I don't think that it is helpful to look for the most technically advanced model, it seems bogus to me. Go for the ones that sound the best to your ears, or perhaps those that give you the most variety in tonality.
All the models benefit from the latest version updates anyway.

Good advice above. It's indeed a tough choice. As for question number one, I'm afraid that's all of them. But the other question might be more enlightening.

What I did is, with the trial versions installed I just played through all of the candidates, spending only a few minutes on each. I then simply chose the ones that had a "love at first sight" quality to that very brief first encounter.

I don't think that's the only good way to do it. But knowing myself, I figured I was best served by making a quick, intuitive decision. I have no regrets about the decisions I made.

You say you only want Pianos, does that mean only acoustic pianos? If you're open to the electric ones, I can also second the Vintage Tines recommendation above. I have never played a Rhodes or Wurly emulation that is this satisfying. Every real Rhodes I've ever played has differences between the keys, and regrettably most emulations smooth those out. PianoTeq strikes a better balance with that, in my opinion, many of the presets feel very genuine to play.

I have the Hohner Electric pianos also. They're a little weirder, and I find myself dialing them in to get even weirder most of the time. The Tines are definitely better suited for most genres, the way they sound out-of-the-box. Since you're a jazz player I guess these might come in handy? Or if they won't, plenty other good options exist.

I am also about to pull the trigger on PTQ7.

For classical pieces, I agree that the Steinway D concert grand piano collection is the way to go.

For jazz, it seems to me that a brighter piano would be appropriate. The Steinway B is a great choice. Although it still has a big sound, it does have a more intimate feel. My personal experience by playing the B is that it also has a fun touch response/playability that translates well to jazz. By the way, the real Steinway B seems to be favored by jazz pianists and it is THE piano of choice at the Jazz Standard club in NYC.

The third piano should be your own personal choice. Do you want a piano more inclined toward classical music or toward jazz? From various sessions of testing and playing, the sound of the Grotrian Grand really captivates me due to its remarkable sympathetic resonances. But I am more into learning and playing classical music.

Oh wow!  Thank you for the incredibly helpful observations and advice!   In particular, I wasn't taking into account the free instruments I'll be getting when I'm a paying customer :-)

Also, I appreciate you highlighting that -- even though I'm generally not one to tinker in this context -- making a few straightforward tweaks may be able to significantly improve how I enjoy some of the instruments.

At the moment, I'm pretty stressed with work and kinda tired, so I'm going to dedicate a good amount of time this Saturday (I know, I know, cutting it close) to do some more playing and listening and deciding and will report back!

Thank you again!

Okay, I couldn't wait until the weekend, so I spent some more hours playing (with headset and also studio monitors) and ended up picking:
- Steinway D combo
- Petrof combo
- YC5 Rock piano

The YC5 is the one I was least sure of; I really enjoyed playing the Studio preset but was meh on pretty much all the other presets.  But I have such nostalgia playing Yamaha grands growing up and I liked the sound and feel for pop & rock playing with that preset .

I'll spend some time on Saturday checking out the non-grand-piano sounds, but my sense is that I largely have those covered well enough for my tastes with my Komplete Ultimate 13 bundle.

Thanks again for all the food for thought and encouragement .  Happy to begin my Pianoteq journey with such a friendly and helpful community!

Good choices and welcome.
As someone already wrote, get the Blüthner too, especially for jazz.

Key Fumbler, yes, heh, I did pick rather "safe" choices but I expect I'll branch out over time as I get a bit more adventurous with this instrument & my music'ing
And completely agree with your take on the YC5; it does seem to have more potential and I hope Modartt will give it a bit more love in the future.

Fleer, yep, the Blüthner was on my shortlist and I almost chose it!  It may well be my next purchase.

Tahlendorf, yes, that present on the Mistral is one of my favs and was a big reason why I chose that pack :-)

Anyway, while I have been stupid crazy busy with work (for a deadline this past Friday), I enjoyed relaxing last night with Pianoteq and -- after spontaneously doing a pleasant ~5 minutes improv -- I was super-grateful for Pianoteq's always-recording option.  Here it is, without any editing (though -- as you can likely hear -- it's far from perfect, particularly with a few overly hard-hit notes that stand out). Incidentally, it's the first time I can remember improv'ing in the key of b minor .  And my experience really highlighted how just fabulously playable Pianoteq pianos are; improv'ing in this situation felt almost like when I was sitting down at a 'real' piano!

I did initially hit a bit of a roadblock:  I was honestly stunned that I couldn't just easily record what I played by hitting PLAY [on the midi file] on the PianoTeq interface into QuickTime or Logic Pro or whatnot on my Mac.  Why on earth does the Mac require a third party program just to record internal sound?!  But the well-respected Audio Hijack program really came through :-).  (Heh, I guess this marks me as an online music n00b, since maybe everyone else already knew about this system default limitation?)

Oh, almost forgot!  The Pianoteq piano in the recording is the Steinway D, "studio" preset (unaltered).

EDITED TO ADD:
Daaaaayum, I had no idea Soundcloud embeds were so huge on this forum.  I really need to do something about that terrible(y cropped) photo

When I first bought Pianoteq it was version 3. I was able to play the version 2 demo for months before buying it. I'd say try the demo version. At the time I didn't have enough space required for the top sampled libraries, while Pianoteq was so novel and easy to use, very responsive, updatable, etc.

There are some demos on YouTube, but you can't beat trying it.
I'd say the Steinway Ds and two others.