I'm not positive, but I'm pretty sure the Carenado 182s were considered suitable substitutes for the MS planes for those GA flights. the organizers had a list of add-on A/C that they considered equivalents of the stock planes...and I'm sure they'll have that listed again too once the site is back on the air.
The P-38s (in particular but not exclusively DCC's) are a very popular race plane. But you will see quite a variety of aircraft throughout the race too. Most of the SimOuthouse team members are usually found flying WWII warbirds but anything from GA & light commercial twins (piston or t-prop), 4-engine piston propliners or bombers, etc might be seen in the skies. Since it's a race against the clock (and the other teams), the faster you go the better you'll do but there are some situations where "low-n-slow is the way to go" too.
The RTW race is a "baton" type relay race as Willy summarized. Once the race begins from the starting airport, a team pilot will fly a leg of the race "carrying the baton" from that airport to one in the general direction of the finish line. That pilot (or his wingman for the leg) has to succesfully complete that leg before another pilot can take the baton for the next leg from it's landing point. A crash or otherwise incomplete leg is considered invalid and the pilot (or another team member) will need to restart that leg from the point of origin.
Most of the team members fly the race online in a multi-player session but it's not mandatory. You can fly a leg offline if your internet connection or computer is not cooperating...the baton's progress is tracked via posts in a specific forum thread so everyone can keep track of where the baton is at. If you can, flying online is the most fun as there is usually several other members online to chat with or give weather reports. Makes a long flight much more interesting!
The usual route for the large ocean crossings in the race is either far north or far south. I.E., the Pacific crossing is commonly flown across from Alaska to Russia and the Atlantic crossing is commonly done via Canada-->Greenland-->Iceland-->Scotland.
In past races, except for a certain few special rule situations there has a time limit for each leg of 2 hours so that pretty much rules that we take these short crossings to meet the time requirements.
I wish I could point you towards the forum threads here from past races but we lost them when the forum puked a while back. Other team members can maybe fill in more details.
Let us know if you're interested. We'd be glad to have ya fly with us!