One remap I can fully recommend is remapping caps lock to control, it's an incredibly natural position to hit the very common ctrl-w,r,t,f,c,v hotkeys.
I don't really care for typing on my Macbook but I do think Magic Keyboard with numeric keys is probably as good as it gets for me. I don't really miss mechanical keyboards at all.
With that said I do agree that modern keyboards completely underutilize the thumb. This is why I love my split keyboard with a thumb cluster. I truly believe every keyboard should have a thumb cluster now. It's crazy that the default is to waste 2 fingers like that.
Using mechanical switches and caps lock for control is better for me, but indeed, stretching for frequent modifiers is bad.
Alternatively you could also try tactiles and the lightest springs you can tolerate and learn to not bottom out while still actuating the switch.