I know this sound like a silly question but I believe you can set the playback frame rate to any arbitrary number in earlier versions of resolve, but not anymore now.
I'm working with some RED footage that I know was shot at 120 fps, and during offline editing I set the frame rate of these several shots to be 120 so that they play in realtime in a 23.976 fps project. Then I did some speed ramps on these clips. And conformed them back to resolve. Obviously they don't conform well. But since the speed ramp data can be properly transferred, now all I need to do is just tell Resolve that these several clips in particular are 120 fps instead of 23.976. I go to clip attribute, just to realize that the Video Frame Rate section is now a pulldown menu, and it has some common frame rates you can choose, ranging from 25p to 29.97 and 59.94, typical stuff, but it only goes to 96... which means there is no way I can set the fps to 120. I used to be able to do this by just simply enter the number there, but not now...
I think you can't do this..
Are you referring to a sort of "interpret footage" function such as in Premiere? where you can dial in a new frame rate to the clip's setting?
Only place in Resolve I can think of where you can set playback arbitrarily is in settings - timeline format. not a clip based function.
Though a useful feature... I don't remember ever having that freedom in Resolve.
(I'd be happy to find out i'm wrong about this one..)
Maybe its worth rendering out the clip with the frame-rate settings baked in then manually bring it to Resolve (you could even consider baking in the sped changes as well). as long as you use a good 4:4:4 codec you should be fine.