> does anyone know a lightweight Explorer alternative?

PowerShell. It's builtin, uses little resources, is fast, has pattern globbing, autocompletion, and can be as efficient as using the coreutils on *nix.

Unfortunately nnn and Ranger don't work on Windows, and the WSL uses more resources than explorer so this workaround isn't resource efficient. Cygwin is very efficient and could be a better solution to run them, I haven't tried it.

edit: Looks like lf works on Windows: https://github.com/gokcehan/lf