I can certainly see the OP's point about the need for FS-related tutorials, if you are just starting out it is important to be able to go from a blank page to a finished model in the sim just so you know that you can do it. Nothing gives the drive to continue learning like being able to taxi past your own first model sitting at an airport. There are plenty of tutorials on Youtube where you can learn to build a beautiful model, which turns out to be completely impractical in the simulator. 20 years ago when the GMAX gamepack first appeared (FS2002?) just about everyone was a beginner, and although there was a SDK of sorts that didn't help those who were trying to learn GMAX at the same time.
There were tutorials back in the old days which showed how to build a simple hangar etc, and place it in the simulator. These included some help with optimisation, and other aspects which the OP asked about earlier -- getting the size right etc. The tutorials I'm thinking of are entirely obsolete now, but in these Youtube days it would be great to see some simple go to whoa intros for very new developers.
However most of that info is available, mainly here at FSD, I'd suggest that the OP deal with his questions one at a time, either through a bit of time searching here, or asking here one question at a time.