You already sound like a P:48 modeler; very particular and wanting things to be exact! I don’t know if you’ve operated on an O scale layout that is designed for operation and meets those standards, but if not, you have a treat awaiting you. There’s something absolutely visceral about the drama of size, detail, mass in operation and the realistic sound (Loksound) when up close and personal. I’ve never regretted the switch.
Rather than try to answer your rolling stock questions specifically, which I couldn’t without some research, I’d direct you to some folks who could. O Scale Resource (an online publication), O Scale Trains magazine, and Jim Harper of Red Cliffs Miniatures- see website (a friend and awesome P:48 modeler) for answers to your questions. There is also a list of all the manufacturers in O Scale, but I can’t recall where it’s located- they would know.
Changing scales is a process best done a piece at a time to familiarize yourself with what’s involved and discern if it captures your railroading juices. It’s more of “builder’s” scale than HO, simply because of what’s available. But that can be a positive vs. negative - if you like to build. So it’s slower, but I find it more satisfying, as does the A&O crew.
Please keep us informed as to the journey. And a couple sleepless nights are to be expected.