It has been my experience that the 80% kits from 1911Builders are pretty straightforward to complete with jigs from Matrix Precision. All the parts come from the same source manufacturer (I think Dasan Industries, same as tr-enabling sells) so they work together nicely. On two of those kit builds I got to a functional gun with no need to fit the barrel or even change the link that comes pre-installed. Now, a barrel that drops in like that is not match grade no matter whether it has "match" stamped on it or not (lol), but they do work pretty well. With those kits, once you've drilled the frame and cut the rails, most of the other parts just assemble together and function fine. With the exception of the thumb safety which will not turn "on" until you've filed just enough of the nubbin down that it can
just barely get past the sear. That's a good thing, you wouldn't want that to drop in because it would then allow some amount of sear movement while engaged.
On those 80% frames it's absolutely critical that you deck the frame to the right height and make it nice and level across the top
before cutting the rails. I do most of the decking with a file and the Matrix jig, then I finish it off with a stone, which is time consuming, but I want it as flat as I can get it. If the deck height is off or it's got a high spot somewhere, your rails will be off and the slide/barrel will sit higher or lower than they're supposed to. That will then screw up your barrel fit and possibly give you problems with the disconnector. Once you have the deck height right, the rail cutting is really very straightforward, just requires the patience to go slow and measure often. If you want it really nice, only cut till you can
start the slide about 1/4 of the way onto the frame, then do the rest with stones.
Now that's just the work to make the gun
functional. There are at least two more really time consuming jobs. One is blending the frame into the grip safety with files and sandpaper. With the parts dropped in the grip safety will probably sit low of the frame so it'll bite you if you shoot it like that. The thumb safety may also need blending to not stick over the edge of the frame.
This guy does a nice job. The other, more subtle thing is that those 80% Dasan frames have a trigger track like a cobblestone road. The top and bottom of hole connecting the trigger guard to the magwell is
rough. You put an aluminum trigger in there and shoot the gun a few hundred times, take the trigger out and there'll be huge gouges in it, which you can feel as grittiness in the pull. Smoothing out those areas of the frame is extremely annoying because it's awkward to get in there. A file wrapped in sandpaper worked for me.
A stainless frame is nice because you don't have to blue it or anything after you're done, just polish it up. Also, get a frame that already has front strap checkering. You can do it yourself but trust me, it's totally worth an extra $40 to save hours of mind numbing work and a cramp in your hand. I have done it on one gun and about 5 minutes into the job I realized it was going to be a much bigger ordeal than I had in mind, but there was no turning back.
To install a match barrel like a Kart takes a lot more work and a few more specialized tools (lower lug cutter, lug file, chamber reamer).