Multisite blog/forum

I’m looking to have a static front page example.com, a blog axample.com/blog, and a forum example.com/forum.

Is this possible or will file locations and URL’s collide?

Could I have an SMF/myBB forum (for example) or does it all have to be with WordPress in order to work correct?

I understand I can do this with sub-domains ie. blog.example.com but prefer to keep the structure like example.com/blog.

Thanks