The rationale behind Sketchup as far as I can see at the moment

I am having a few issues, as a beginner, which with time may prove to be not quite right, so read on with that proviso. Especially that poor soul on the Sketchup team whose job it is to monitor stuff like this.

1. It seems a bit iffy that you model in one program , and use another to produce output. People obviously cope with this, so this could be just pickiness on my part.

2. You put a window in a "wall".  Great. Not so great if said wall is 2 surfaces, because then you have to dig another hole in the inner surface. Not so easy if other things are in the way. Throw in the situation of a brick veneer and a timber stud wall and suddenly windows get very irritating.

3. You want to do nicer windows? Easy, just download and install a plug in that does this. Oh wait....anything any good costs $$$.  Some of the free ones are not up to date. Want a roof tool that means you just pick a surface?  Can be done, except the one I chose said no way to the roof in this picture.  So it had to be built in pieces. It turned out I had made it too big anyway.  Vali Architects put out some nice stuff. Just $118/year.
Tempting but at the moment I am just trying to master the basics, so drawing things from scratch is the name of the game.

4. Just saw a Youtube where a man is manually putting on ground lines.  Surely this is the goal of 3D to do away with this sort of madness?