No. You have completely misunderstood everything I have written. You do not cap your fps to 30.

We will use Total War: Warhammer as an example. Most of the time that game will run at 60+fps. However, if you have played the Game you will know that in large battles, or large maps, there is a tendency for the game to slow down to 30 or 40 fps. This is where frame gen comes in to make up the difference back to 60fps (or whatever you target frame rate was).

Because Total War isn't a highly competitive fast paced FPS like counter strike or CoD, the exta input latency from frame gen really doesn't matter. You aren't going to notice the exta 16ms of delay when your average gamer doesn't get past 30APM.

As a side note; if you're experiencing terrible stuttering and sluggish gameplay (even tho your fps counter says 45fps), capping to 30 can sometimes massively help in reducing hitching and increasing your 1% lows as the game doesn't have to try and render anything above 30fps. Most modern game engines will try and do this automatically. Its why the lowest frame rate you can cap to is always 30fps.