We use the dataloader pattern (albeit an in-house Golang implementation) and it has solved all our N+1 problems.

E2E type safety in our case is handled by Typescript code generation. It works very well. I also happen to have to work in a NextJS codebase, which is the worst piece of technology I have ever had the displeasure of working with, and I don't really see any meaningful difference on a day to day basis between the type sharing in the NextJS codebase (where server/client is a very fuzzy boundary) and the other code base that just uses code generation and is a client only SPA.

For stitching we use Nautilus and I've never observed any issues with it. We had one outage because of some description that was updated in some dependency and that sucked but for the most part it just works. Our usage is probably relatively simple though.