In my humble opinion, these schemes have little benefit. I once went round a drawing office and asked the draughtsmen which they used. They said (typically) "that's something we learned at college but don't use in practice". First and third angle projections are suitable for objects whose overall dimensions are more or less the same in each direction, facilitating the various views to be shown on one drawing. But life isn't like that. You get long thin things. A better practice is to show a plan, and on the plan label the position of any cuts or elevations and which way it is looking. The view of the cut can be an any part of the drawing or even another one. I've never had any trouble with that. Going to the length of being pedantic about it is all very well when you are learning to vizualise at the beginning of your drawing practice. As for isometrics and obliques, I think they can be more confusing than illuminating. I prefer perspectives. With something like 'sketchup' you can choose your point of view to be most communicative for your situation. Get real, I say.