I replaced my NEO 1 with a NEO 2T and continued to train with the exact same FTP, so no “underestimation” issues there for me, at least from what I can tell by RPE.
I would describe it as “more responsive” and not as “more aggressive” compared to the NEO 1.
The only issue I had: the left/right cadence sensor (introduced with the NEO 2 series) was not compatible with my MTB setup, I needed to extend my left crank. Tacx provided me with an extension set, but I prefer my DIY solution.
It’s pretty boring, it just works.