The only thing I can help you with is the T-molding question. (I'm a cab-building newbie, but a long-time woodworker.)

You don't say what sort of wood you'll be using, so I'll assume plywood or MDF. You asked if you had to use T-molding or whether you could just round over the edges. The short answer is "yes"; the longer answer is "yes, but..."
If you are using plywood, you will see the various plies on any exposed edges. This may or may not be acceptable to you cosmetically speaking. If you are painting your cabinet, it will likely be less obvious than if you are staining it or using a natural finish, either of which will show the plies quite clearly. Even if you paint the cabinet, you'll want to use a good wood filler to seal the pores in the edges so you get an even finish. Plan to seal the wood, apply one coat of primer, seal again in case you missed any spots, then two (or more) finish coats.
If you're using MDF, you definitely need to do something to seal the ends -- MDF soaks up paint on the "end grain." A good method is to thin some Bondo (or other polyester body filler) and apply it generously to the end grain. When it's dry, sand it carefully, then apply the primer (oil-based! MDF and water don't mix!). Then any compatible top coat(s) for the final finish.
Hope this helps.
-- Chris