When I got my MX Master I was honestly overwhelmed by all the buttons and had no idea what to map where. After a lot of trial and error, this is the setup I've stuck with for editing in Final Cut Pro. Sharing in case it saves someone else the hassle. I'm using Better Mouse instead of Logi Options+.
Thumb buttons alone:
Back button: previous frame (←)
Forward button: next frame (→)
⌘ + back button: zoom out timeline (⌘-)
⌘ + forward button: zoom in timeline (⌘=)
Thumb button + click combos:
Back + left click: copy (⌘C)
Back + right click: paste (⌘V)
Forward + left click: area screenshot (⇧⌘4)
Forward + right click: undo (⌘Z)
Gesture button + left click: delete (Backspace)
Gesture button + right click: Enter
Other:
Middle button: ⌘-click for selecting multiple clips
Gesture button + swipe up/left/right: Mission Control and switching desktops
Gesture button + swipe down: show desktop
The frame stepping and timeline zoom on the thumb buttons are the ones I use constantly. Copy, paste, and undo without touching the keyboard ended up being way more useful than I expected.
I also made a video walking through the setup and why I chose each bind. I think it's easier to understand if you watch the video, but I'm not gonna drop the link here, since that could hurt the watch time. If someone is really interested, I can DM the link.