You,ve got a good engine picked out for your 4* and you'll get a lot of satisfaction building it yourself. For your first build and low wing , IMO your could,nt done much better.
And yes 4 *'s are a dime a dozen at the feilds and rightty so. They are simple to maintain , the upright engine and open check design puts everything easy to get at. This well be your first build, low wing, and taildragger. If you nose over on an inverted engine, it's not pretty. And if your like some of us, your second plane is going to take a beating but at the same time your going tolearnalot.
I would build the 4 * stock, besides beefingupfuse right behind the wing saddle, beefing up the landing gearmounts, and adding an extra hinge to the ailerons so you can easlyremove a bay, after you get some time under your belt.Keep it simple, learning to fly the 4 * , then Mod your 3rd plane the way you want it . You'll have a build under your belt and also know what style of plane you like to fly.