Lots of questions sprung in this thread. Sorry if I missed some.
Overbag to prevent condensation. I think the idea is to use VBL liner inside the bag. I have one and I use it in extreme cold situations. It adds warmth and it blocks moisture that comes from your body over the course of the night. Your body's moisture is usually bigger contributor for wetting out a sleeping bag over consecutive nights. My VBL liner is not extra long ... i.e. I only have it up to my chest. It has fuzzy fabric on the inside which helps to feel comfy. I would only use an overbag if I used a VBL liner as an overbag further traps the moisture that comes from your body and contributes to dampening your insulation. I suppose this only applies if you use down.
Stripping to sleeping clothes - yes, most of the time. When I get to camp I stay in my current clothes while I prepare the sleeping quarters, make food, gather wood. This low exertion activity maintains my body warmth and helps drying out the damp/sweaty hiking clothes. In the meantime I also make a hot water bottle and slip it into the sleeping bag. Then I use mini pad that I use for sitting (foam pad) and I stand on it and strip completely and put on my sleeping clothes - sleeping clothes are usually my second set of insulation layer that I carry with me in case of falling into water etc... - then I slip into my sleeping bag which is now toasty warm from the hot water bottle. Is stripping and dressing in sub zero temperatures cold? YES. Do I sometimes shake from the cold during the undressing and ressing ? YES
But I got a warm sleeping bag waiting for me.
I do put some of my wet clothes between my pads. It works , somewhat, but more importantly it's probably the best place to stuff it anyway ... better than letting it freeze stiff.
Multiple pads? YES. At least 2. Sometimes 3 is better. Foam on the bottom, insulated inflatable on top and foam on top - a sandwich.