Recording to later play on YouTube (or others)

Good news, the answer is a total YES, with a couple of cautions:
1) check that the tempo of the midi file has been embedded properly
2) you will need to set an appropriate velocity curve in Pianoteq
Apart from that, you should be good to go!

Yes, that's correct, set your velocity curve just as if you were using your piano for live input. The velocity curve affects midi playback - that came as a shock to me when I first discovered it! Try switching between the factory preset curves while playing a midi file and you'll see what I mean. The raw data doesn't change, but it gets filtered by the velocity curve.

Don't feel bad about it, it took me quite a while to understand the velocity curve - I think a lot of people struggle with it. The Calibration Assistant is far from perfect, as you have found out! You may find that somebody has posted a good curve for your piano in the Keyboard velocity curves section of this site: https://forum.modartt.com/viewforum.php?id=10 . If not, your best strategy may be to choose the factory curve that seems to work the best (for example 'Moderately fast keyboard') and then try manually adjusting it. Record your own midi file with a good dynamic range, then play it back, adjusting the control points on the curve as you go. Click on each point and use the down/up arrow to adjust it. Make very small adjustments, aiming to make it sound as natural as possible. I hope this is helpful. There should really be a lot more documentation on velocity curves IMO.

Ah yes, it does look very mysterious, but it's simply a matter of copy and paste. Just copy the entire line that says 'Velocity = ...', then open the Velocity menu in Pianoteq and select Paste. Your velocity curve should appear, and you can save it under any name you wish. To understand what's going on with the curve: the first set of figures = the raw input data, the second set = how these are 'translated' in Pianoteq.
A simple example:
Velocity = [0, 32, 53, 70, 127; 0, 34, 56, 70, 127]
This means that input velocities below 70 will be very slightly boosted, but above 70 they will be unaltered.

Well, for sure, something positive has ocurred thanks very much

Miles away from being a sound I would die for, but "I think" for sure every single different piano sounds now better than before, or even way better YET as I say, being VERY VERY VERY far from nothing special but the differences are there for sure. At this point, my head and ears are almost damaged so I think its time for me to quit for today and make a fresh start tomorrow with this new setting. Tomorrow I will probably be able to further explain other problems.

But again, somehow, once again, Im sort of leaving the subjet of this thread which were recording and looking more again for my real main interest which is playing taking advantage of Pianoteq sound

Will see tomorrow... thanks very much Dazric

I am glad that you have already been helped with this issue. I also couldn't figure out the speed curve for a long time. Honestly, it seems to me that I can still make some mistakes when I set it up. However, it has become much better compared to my first attempts.