Strats are a good kit to start with. I just completed a Strat project, and the great thing about them is that if everything lines up in your dry-fit, it's likely to go together well. Also, there are probably more after market parts available for Strats and Teles than any other guitars on Earth, so you can customize about any way you like.
For a future build (there always seems to be a next one) if you like one of the righty kits, consider asking Adam if he can custom order it as a lefty, or alternatively, if a symmetrical kit liken an SG, with the control cavity un routed/drilled. There is a lot of stuff that he can get "off the menu" as long as you are willing to wait a few months to get it. I like Jazz bass necks better than P-bass necks. Adam was able to order me a Jazz neck for my P-bass project. It took a while but was no problem.
Most people here will give you 2 pieces of advice to start with: (1) start a build diary--a great way of getting help even if you didn't know you need it ;-) (2) Do a dry fit to make sure everything fits and nothing is missing. If anything looks odd, folks on the forum will be more than willing to help, and Adam is very responsive as well.
It must be a pain, but as Fender3x says, there's a good chance of getting a L/H custom version ordered of some of the kits, especially if it's a symmetrical shape (strictly speaking SGs aren't symmetrical as the top horn is a bit longer than the bottom horn, a carry-over from double cut LP specials). But an ES-1(ES-335 style) body can easily be drilled for L/H controls and bridge slant and a L/H nut fitted.
The problem for PBG holding a lot of L/H stock is (IIRC) that the minimum run order for a type is for 100 guitars, so if you had a L/H version of most of the kits, that's a lot of extra stock to carry and store which is going to take roughly 10 times as long to sell as R/H models. Of course it could be a chicken and egg situation, as if there isn't the stock, then people aren't even considering asking about other L/H model versions. Email Pit Bull and ask.