Great to hear that :)!!
Thanks Nikolas for answering regarding Prisma! The reason why we chose Prisma is because it is declarative, which plays really well with Wasp, and because it supports multiple types of databases - for now only relational, but as Nikolas said, in the future also nosql.
Regarding TS - you are right, TS is a better fit for this than JS! We started with JS, but plan is to switch to TS real soon, for the reasons you described. Here is the Github issue discussing this: https://github.com/wasp-lang/wasp/issues/143 .
If you don't mind me asking, how big is your team / what are you using right now to build web apps?