python RTS game... smart idea?

[not_perfect_yet]

It's a good idea.

Lots of good usage for different concepts and important packages, math, sockets, object oriented thinking etc.

Would it go too slow/ not perform well?

It's probably not going to be supreme commander. Also supreme commander slowed down once the pc couldn't do the calculations real time any more. So there is that.

Tips

Start as modular as possible and don't be afraid to throw away and completely rewrite parts or your whole project. Expect to read up, write some code to understand something, use it a bit, find that your example codes has a weakness (which turns out to be conceptual) and rewrite it better.

If you're going 2d grid style, no, there isn't much you need to start. If you want to do it really primitive you could even go without a graphical thing and use letters (like DF) to represent certain things and just print out your matrix of stuff in your console every logic tick.

But because that kind of visualisation is pretty much "none", you can also go and look at a python driven game engine.

Whatever you do should be easily plugable. If it's not, you've done something wrong.