I think Karabiner(-Elements) is way more popular and probably more flexible, but I've had a lot of success with Ukelele for 6-7 years. I exported one layout and just copy it to each new macbook. Specifically it lets me set `option` as a dead key so I can have `opt+i`, `opt+j`, etc... shortcuts in editors.
https://software.sil.org/ukelele/