starting off with fh5
at 65 fps with %99 gpu load, we have 47.6 ms of input lag, which is actually really good, there are worse games with worse behaviours
when frames are capped to 55, indeed we have reduced input lag
god of war
so at 68 frames with max load, we get 50 ms input lag, which is not that bad, but can be better
reflex reduces the framerate, but also drastically reduces the input lag!
finally we have manual 56 fps cap which has similar lag to reflex
to my understanding, its practically doing the capping based on GPU headroom on the fly, which is very useful
as you said however, steady input lag may be more preferrable. and then again, it may also be hard to attain specific performance levels at times, especially on PC where most games lack proper dynamic resolution scaling. on consoles i guess what you want is very much feasible with dynamic resolution