My advice would be the following:
For matching hipfire, use 360 distance unless the game's meta is heavily predicated on aim, like an FPS game. If you just want familiar 180s and 90 degree turns. It's pretty much always best to match 3rd person games with 360 distance for example, since 3rd person aiming is different anyway. For FPS games you should really be trying to match hipfire FOV anyway.
0% Monitor distance (or focal length), maintains the actual sensitivity at the point of aim. This is generally the most useful for ADS transitions, especially in games where there is a lot of tracking, recoil control and / or slower ttk.
For games with high zooms and more sniping-style aiming mechanics (or at least where they are more important) use a monitor distance conversion - depending on the amount of zoom anywhere from 50-75% horizontal Monitor Distance will probably feel the most natural. Focal length generally feels too slow compared to hipfire once the ADS FOV change gets to be greater than 40 vertical degrees or so of reduction.
This is why it's really great when games give per-scope ADS sens control, so you don't need to compromise.