I built a couple of these American Standard kits many years ago. Still no sag, warp, or melt down

Glues probably used: 5 min epoxy, wood glue, CA. In addition to the glues, Testers Plastic Putty was recommended for filling gaps between parts. Cars were air brush painted with Floquil (the original).
Cars with wood roof probably could be assembled either way. As the cast roofs tend to have a bend, they should be glued to the sides to keep everything straight. I prefer to have the roof and sides joined anyway to keep light from showing through the seam.
I have my own "batcave" stock of a few more of these kits to build "one day". I opened one to check what was there for instructions. There were two sheets of paper printed both sides with "applies to all kits" type general assembly stuff plus a drawing showing the interior arrangement. Let me know if you would like me to scan and email you a copy.
For lighting I would now use LEDs. The HO guys have ready made LED lighting strips if you didn't want to wire up your own.
Extra detail parts and interior kits are available from Keil Line.
Charlie