Update:
Upgrading to version 7 from 6 is seamless! Activation of your existing serial is required for v.7, then it finds the (custom in my case) presets folders you have set in version 6. The equalizer setting I mentioned was readily applied. So, apparently, settings such as EQ and Velocity curves are interchangeable.
Detail, regarding "frozen parameters":
Later on, I separated the presets folders for each version (choosing a different folder in the settings) because I thought that re-using the v6 ones created an issue with the "frozen parameters" option. This separation, however, did not solve the issue. Either "frozen parameters" works differently than I expect or there is a bug in v7. I explain:
My expectation with "frozen parameters" is that, once set, no matter what instrument I choose - including unchanged default ones - the, e.g., equalizer, setting will remain fixed. For me this works but then does not persist through program restarts. So, next time I start Pianoteq, if I switch to a preset I haven't explicitly saved with my EQ setting, I will get the default EQ