The nice thing in this case is that Django will meet you where you are with your preferences. Want to go the manual route? Sure. Want it to take a shot at auto-generation and then you customize? Very doable and. Want to let Django take the wheel fully the majority of the time? Sure.
> what happens if you onboard a superstar that works with django some other way
If you hired a "superstar" that goes out of their way to hand-write migrations in cases where Django can do it by default (the majority of them) you did not in fact get a superstar.
I have yet to see anyone hand-roll migrations on purpose. In fact the problem is usually the opposite, the built-in migration generator works so well that a lot of people have very little expertise is doing manual migrations because they maybe had to do it like 5 times in their entire career.
Either way the end result is a single file in migrations/ that describes the change, though you do have to write it with Django's API if you want further migrations to work without issues (so no raw SQL, but this low-level API is things like CreateTable() and AddColumn() - and is what Django generates automatically from the models, so the auto-generated migrations are easily inspectable and won't change).
No. Django is very good at having the autogenerated/default stuff be consistent with what you do if you want to write manually, it's not one of those "if you want to use the magic as-is it all just works, if you want to customize even one tiny piece you have to manually replicate all of the magic parts" frameworks.
is this like the "it takes 50 hours to set up a project management tool to work the way you want"? what happens if you onboard a superstar that works with django some other way?