how do I switch option + f to [next word] instead of ƒ on macos high Sierra I want to switch option + f to [next word] instead of ƒ. How do I do that?

For example in the bear text editing app, I’d love this affordance. 

How can I change the key mappings or make this a shortcut on macOS?

Or for example I would like to delete a word with option + d, instead it prints out the useless ∂
All those shortcuts you mention work with control+_. So either you can remap your option key to behave as control, or make yourself habitual of using control.

https://support.apple.com/en-us/HT201236


Swap CMD and Alt only on external keyboard 
How do I remap a key in macOS Sierra, e.g., Right Alt to Right Control?