Need guidance on 301 redirects – Is it Domain Mapping?

I’m confused about this topic, and I would appreciate anyone who could give me a hand. I purchased several domains, and I’m using say maindomain.com as the primary domain for WPMU with Buddypress. Now, I would like to have the other domains, like otherdomain.com, and anotherdomain.com to all point to the primary domain. I read online that the best practice is to use 301 redirects.

1. Will the domain mapping plugin accomplish this? Would I also need to change any settings on my domain manager?

2. When users create blogs, like myblog.maindomain.com, would it be accessible via myblog.otherdomain.com or myblog.anotherdomain.com?

I hope I made sense

Lucy