I have the LC1230. I think you will be very happy with it. The saw is capable of cutting extremely precisely. The only thing holding it back is the clamp (it's not really bad, the blade is just capable of cutting on the level of thousands from flat, and the clamp isn't really on that level.)
Keep in mind, the blade can be sharpened, if I'm not mistaken. I've probably done at least a hundred cuts with the stock blade, (everything up to 4" square 1/4" wall tubing, 1"x2" bar stock), and I just ordered a new blade yesterday (planning to try having the old one sharpened).
If you really want to dial in the angle of the clamp, the best way I've found to do that is to make a test cut, check against a 90/30/45 degree angle or whatever, and then adjust the clamp as necessary, make another test cut etc. Using this method I've been able to make cuts that I believe could be as good as +/- .005" perpendicular across a 2" tube. At that point the sides of the extruded tube aren't really flat anyway, so there's not really any point in getting better. The actual flatness of the cut is much better than I can measure without more sophisticated equipment.
For cutting square with a grinder, I've found the best way to make an in plane cut around a tube is to position one eyeball (equipped with safety glasses, of course) directly in plane with the blade, so that you're just looking at the edge of the blade and it appears to be only 1/16" thick or whatever. Do the same thing with your cut once you get started. Then just focus on keeping the blade and the cut in-plane with each other as you work around the tube (for smaller tubes, you can just cut from one side, which is nice). Using this technique, my limiting factor on accuracy has been how accurately I can draw lines on the tube. Even with the chop saw, I still end up cutting some stuff with the angle grinder, though if it will fit on the Makita, I will cut it on the Makita.
Cutting 4" tube: