Yes, it's better to disable the rls extension and stick to rust-analyzer one. There's some preliminary support for rust-analyzer in the rls extension, but it is preliminary.
It's hard to say what exactly doesn't work here. I suggest trying simple hello world projects and steps from the troubleshooting section:
have you checked your CPU/usage? sometimes with more complex projects or slow CPU, rust analyzer will take some time to analyze your program before it starts being helpful.
Also just found out. on Windows 10 + vscode + Rust Analyzer plugin, if you are using WSL v2 with Ubuntu 20.04 and when you launch code . inside your wsl terminal.
Rust works flawless. It even started to show me clippy suggestions which I could just fix it with ALT + ENTER
And I'm able to give build and run that code from windows folders as well. C:\Users\ajink\RustProjects\pipeviewer