IM - Solo or Pack

As long as you are not breaking the rules i.e. drafting or blocking do whatever you feel like. Some people draw pleassure from competing against others in their AG for top places, others against themselves vs the clock and other like to participate. Do your thing, don't break the rules on get on other racer's way and have fun.

I wouldn't plan to race with a friend on race day.

If you end up staying together, great, but if you plan to you one of you is feeling fast and wants to take off ... it could create some race time hostility/ anxiety. (or if one starts to fall apart ... does the other want to stick w him/her?)

I agree. You never really know what that days has in store for you and it would be hard to think you could stay together and all be happy for an entire IM.  My running partner and I train together but on race day we both do our own races and are happy for each other whatever the results are.

If you choose to race together you have to have predefined rules on what happens if someone has to stop (bathroom) or if someone is struggling, etc.   I think it would be hard to race the entire IM together, but if you are about the same speed and came across eachother on the run, it might work.

i have absolutely no idea how 2 people would get out of an IM swim near each other.  PennState and I got out of the IMLP swim first loop with in seconds of each other...and had no idea!  2000 people in the same caps and black wetsuits....have fun attempting to stick together!  But as others pointed out, b-room breaks, stops at special needs, etc, it just seems like it'd be tough.  If it were me i'd say each do your own thing, and if you wind up leap frogging each other on the bike by chance, have fun with it.  If you end up running part together, awesome, but i would just let it happen if it does rather than plan for it. 

The hardest part IMO is if one of you is doing well mentally & the other isn't.  Other than a quick few words of encouragement, i kind of avoided anyone that seemed down, wasn't smiling.  It's just too easy to get there yourself when everything is hurting.  It takes work in an IM to stay up, and i'd be way too nervous about being brought down.