Also, any tips & good practices are greatly appreciated :)
I think you can manage to find something about this topic. it's pretty popular one. ex: https://www.educba.com/c-sharp-vs-js/
Something I don't see discussed enough over the internet is the performance difference. I don't think you should worry about this. 95% of the time you won't notice the difference on your day to day projets. You will know what you need in terms of performance when you get there.
If you want to learn
C# to write some backend code you can also check out
A good entry to
Express.js. It is the most common web framework for
Node. It's well documented and there are a lot of educational materials for it.