Yes, you can link to your site from your forum. You will just have to have two registrations. When vShare 2.7 comes out, I actually plan to integrate it into SWF forum for my own site.

As for the site, yes, it will be blank with the default skin (similar to the vShare demo). You can have whatever type of videos that you want on your site. It's your choice. The site has an admin panel. However, there is only one admin account. You cannot have moderators or multiple administrators.

As for your specs, those specs should be fine.