Hmmmm . . . Compact and portable?
Choppers do a nice job on most wood, but they weigh a ton. They do have the advantage, in the small shop especially, of being quiet and dust-free, When I have to move mine more than a foot-or-two, I call Two Men and a Truck and they send three men.
I suppose the most compact saw setup would be a ten- or twelve-inch miter saw with a commercial or home-made measuring bench, but it's not something I'd want to lug around too much, either. The saw is portable but, but when you add the bench . . .
Oh, wait. I DID cut frames for a while (before I had a shop) with a good quality carpenter's miter box and backsaw. It was very compact, very portable, very quiet - but the corners weren't very good and, if I had been using some of the bigger mouldings, I'd still be sawing my first frame thirty years later.
I'm not making fun of you, but I don't know that such a thing exists.