Getting started (on Linux)

Hey!

I just found out about KSP and really want to get into it. However I'm a bit a confused about the best way to begin. Here are some questions about the setup:

1. Apparently KSP2 isn't all that great and I should just get the original game?

2. Given I did that, should I get DLCs? Do they add meaningful content or are they just overlapping with mods?

3. Mod recommendations? Not looking to make the game needlessly complicated, but just the kinda mods that a beginner would consider improvements.

4. Install method? Steam Linux version, direct download Linux version or windows version through Proton?

Thanks!

PS. KSP is on Steam sale until 11.9!