How will I know if someone is ban evading?

Hi, I manage a small subreddit and recently banned someone that was being a nuisance in the community towards other users. Account looks to be an alt account.

• How would I know if this person joins with another account, specifically how do I make use of the Ban Evasion tool?

• Will I get alerted that a new member is actually a banned user evading a ban?

• Will Reddit automatically suspend this user without telling me, or will I have to manually do it?

• When would it count as ban evasion, when they join the sub, when they vote in the sub (upvote/polls), when they comment/post?

While trying to search these questions up before making the post, I saw a few posts here about how the ban evasion tool is unreliable.

-Can I choose to not ban a user in the first place (like whitelist) if my intuition tells me it’s a false positive?

New to this so sorry if questions seem basic. thanks in advance