sounds interesting to me what you all doing, hope its not complicated or a idiot like me will /1 /1, lol.
It's not complicated. It's just time. SMF set up is about as easy as they come, and if you've got a decent host, a lot of times, they will walk you through third party set ups. However, they've already gotten past the "hard" part which is launching the forum - now they are just dealing with tweaking it - and that's not hard. It's just time consuming. Only advice I have is to not go overboard with the mods. It doesn't matter how fast your host is, how much bandwidth you pay for, how how much tweaking you do - if you add too many mods, you will ultimately slow down your site and members will be crawling. So be picky about what you integrate, and open a TEST forum to apply those mods BEFORE adding the mods to your actual forum. That way you can see how each mod will interact with the others. Otherwise, good luck and can't wait to see your unveiling.
SMF is the easiest forum software to use. I've personally used phpbb, vBulletin, e107, and a ton of other small ones and SMF is about the most functional and easiest to configure. Minimal code editing and trouble shooting and their package installer makes everything simple. Most of the time spent setting up any forum is getting where it works for you or your members.
Mods can slow down the forum, depending on what they do. Some of the ajax mods run more processes, which slows the forum down, while others that get hard coded are lighter on the system, others just change what is shown on the forum and don't slow it down much at all. The last forum I had, had over 50 mods, a few custom and 8 user selectable themes. Ran a bit slower than a fresh install, but not noticeable to most.