Hi and welcome
Thats a lot of questions in a small message! The forum is a good source of research and if you try a search at the top with some of what you are asking you'll find some great discussions that have taken place on here.
Most of what you're asking are particular "no right/wrong answer" type questions;
150 vs 204
DSG or Manual
4Motion or 2 wheel drive
New / Used
It all comes down to what you want to do with it and how much of a budget you've got.
As a guide, we started off thinking a 150 Manual (new) with only a few options but we have ended up ordering a 204 DSG with quite a few options in the end. We figured that we're planning to keep it a long time so need to get the spec right now and have no regrets later.
Best advice is to try a few. You might find the 150 manual is all you ever dreamed of, or, you might find it needs more go and you don't like all the gear changing. Ergo, 204 DSG etc.