While I use a X-Pro 2, the AF system is similar to the X100-F's.
Learning all the AF functions with dual-finder FUJIFILM bodies is daunting since the EVF and OVF methods can be slightly different. Also, some of the AF modes are intended for video (which I never do). Here
is a guide FUJIFILM wrote about the X-Pro 2 AF system. Most, if not all of this information is relevant to the X-100F.
I use the OVF ~90% of the time. Whenever possible, I focus the camera as I focused optical RF film cameras (focus and recompose). I mostly use the M AF mode and invoke focusing manually with the AFL button. The fly-by-wire lens collar focusing is now a practical option. I also use the Electronic Rangefinder window to conform focus. I prefer the red focus highlighting to the split-screen simulation.
Occasionally I use AFS mode with a shutter half-press. I never use AFC because it wastes battery life. I never use PRE-AF for the same reason. Both modes continually adjust AF no matter what you do.
Face detection works well and can be useful when one person is in the frame or when multiple people are within the intended plane of focus. It is quick and focus is easy to confirm using the ERF. For posed portraits, the Face Detection Eye mode is worth a try. Note, face detection does not use any of the phase-detection focus points which could affect focus performance.
Always use the mechanical shutter. In ES mode the camera can not focus in between shots.
Always use High Performance Mode: ON. (Power Management Settings). Otherwise AF performance will be compromised.
Make sure the Zone AF box is large enough to covers all the phase detection pixels. With single point AF make sure AF-box is set to maximum.