I know what you mean, I have tried some of the newer sub 0.10s high torque servos for both steering & throttle & I just found them way too sensitive & twitchy for my liking. Couldn't really use them at all unless I dialled in negative expo to compensate & relax things around neutral.

Now I'm running 5955/7955, which are identically spec'd at 0.15s 24kg (for me they're actually about 0.135s 26.5kg running on 2s LiFe) & I'm able to drive with much better accuracy, able to modulate throttle & brakes with so much more feel & ability to make the tiniest of throttle/brake/steering adjustments while driving that for me there's no point having the fastest servos or even anything faster than 0.10s.

I never tried using the speed adjustment setting on any radio, always used expo as what we (I) want is more control, not necessarily slower overall servo movement. And the way negative expo works, dulling near-neutral response & progressivly returning to full speed towards the end points is IMHO what is required because by the time a control is at the end of its travel, eg at or near full lock steering or full throttle, usually tiny, small changes are not required. When near full lock, it's very unlikely one would need to either add in a tiny bit more lock or remove just a tiny bit of lock because with that much steering angle, the car will only be in that specific situation for a tiny portion of 1 second. As in, turn into corner, dial in more lock & if anywhere near full lock you'd need to extremely quickly start relaxing on the steering or the car will loop out.

But with this sort of adjustments there can be no firm rules as it is 100% determined by only the driver's opinion & more importantly feel. Doesn't matter what works for anyone else or whichever champion if ti doesn't feel right or comfortable or easy to control for you or me. Hence the need to just try things out. For sure ask others what they do & why they have chosen whatever settings they use but still comes down to trying it & seeing if in one's own circumstance an improvement has been made.

Hope that helps you more than it confuses you.