The proces on https://join.the-nostr.org/ (just a demo, do not use it) is rather smooth, only that this does not explicitly give you the underlying privatekey, but it is actually stored locally so trivial to add.

You 'need' an active signer only if you want to be part of the multisig. Not sure how usefull that actually is, you only reduce the trust a tiny bit. Its still a threshold signature so collution is still possible so at the end of the day you still trust those that you made part of the FROST.

So no, you dont need to be an active signer, you just get a bunker link and you are off. If the link gets compromised you can ask the signers to stop signing and create a new FROST based on the same key with the same resulting Npub