My old Stac Zero Halcyon offered no resistance at all downhill, and spinning out with no resistance was extremely unpleasant. I was concerned that the powered downhill of the Tacx Neo would be even worse, but in fact it offered about the right amount of resistance once I'd moved to 52x11. To quantify, on the Copacabana ride my max cadence was 116 at the top of the long descent, but that soon settled down to just below 100 - by then I was on a solo TT effort to hold off the chasers. Not being mechanically geared the Tacx Neo Bike is more of a spin bike and perhaps that's the rub.
Have since remembered that my Rossin road bike is 52x12. With 11/13/15 I often feel between gears so 12/14/16 might suit me better on rolling terrain. However, whilst I hadn't considered 116 cadence as 'spinning out', 120 is considered the upper limit for most cyclists, so it's got to be 52x11 on the trainer for me.
Of course there's that thing the French call 'souplesse':
https://www.cyclist.co.uk/in-depth/souplesse-the-art-of-perfect-pedalling
