Default Set Up / Settings - USER PROFILES

Hi

I love this theme, it's awesome.

What I need to know it managing my sign up users to prevent bots and spammers getting onto the site.

What are the the default settings to have so each user has to be authenticated before they post to the site?

1) Worpdress Settings "New User Default Role"
2) can we add in CAPTCHA tool to stop robots?
3) any other settings in them options?
4) Should I have "anyone can register" switched on in WP Settings?

Once they are signed up, i'm OK with them adding in anything they like.

Thanks.

P/