In my experience, most people who complain about TS slowing down development are devs who've been working with pure JS for a while and haven't gotten over the (relatively brief) learning curve to adopt TS.
Migrations, however, are always painful:
1) You're going to end up writing code that ends up being difficult to type later; to the extent that you and every single other developer on the team is disciplined enough to avoid that, you may as well adopt the typing ahead of time
2) The support & tooling for managing "halfway" migrated JS -> TS projects "exists", but is obviously inferior to just "buying in" all the way
If you haven't put in a huge amount of work yet, I'd strongly suggest pivoting to Typescript ASAP. I don't know how Vue handles it but it performs beautifully for React.
