You are in the Nim forum, you know (inside?) that you definitely want Nim
instead of C++. If you have looked into C++ for your backend, what are your
findings, which libraries would you depend on? the Nim eco system is quite
small, see if there are matching libraries in Nim see:
<https://nimble.directory>/ or ask in the forum, if you can't find. otherwise,
you will need bindings, and there are several options for that in Nim. If you
intend to write most of it yourself, then i'd sure jump ahead and start with
Nim. It's a language that adds very little complexity to your code, so in a
long term, you can stay productive. But, tooling and ecosystem will not be as
good, and u should know this before.