To the best of my knowledge option left/right in macOS is identical to ctrl left/right in windows for forward / back by word. holding shift allows for selecting text word by word.
Using option left/right works in every other macOS app I have tried except obsidian. I find it very unhelpful to only have command left/right (equivalent to home / end) and letter by letter navigation as the only options.
Things I have tried
I looked in the keybindings as well as searching google, reddit, and the forums, but I only saw people saying it’s an issue and asking for help with this issue.
I will not be able to use obsidian on my new Mac if I cannot efficiently navigate and select text.
Obsidian Sync has a setting to not sync hotkeys between certain devices (the {VAULT}/.obsidian/hotkeys.json file). I don’t sync my hotkeys between win and macOS devices for the reason you mentioned above.
Other than that, I don’t know of a vanilla way to prevent sync or have it be more granular than the entire file. There may be a plugin that can handle this.
What do you use to sync? I know with Syncthing and git you can ignore/exclude certain files from syncing. Maybe there’s something to investigate there.