Frame rate 90 FPS issue

Hello!

I've got some feedback requiring our game to perform at 90 fps on Rift and 80 fps on Rift S;

Is it required to perform at this level for all quality settings?
The graphics options in the game enable  the player to choose between different graphical qualities (from low to ultra).

So do we need to ensure that a solid 90/80fps framerate for both the lowest possible quality settings as well as for the highest possible quality settings?

thank you in advance
Fabio