Bob, considering your operating objectives The Kadees (or equivalent) will serve you best. Kadees body mount easily to most AM and MTH freight cars. The AM passenger cars have body mount pads but using the passenger car body mounts will impose minimum radius requirements on your layout track plan. I suggest you test the cars and engines you plan to couple together before laying out the track.
The Budd cars with Kadees should work on 27”R track and #5 turnouts. If you buy the full scale 80’ AM sleepers they work on 27”R track with the truck mounted couplers but not with body mounts. I tested the AM 80’ cars on my layout with body mounts. For 100% reliable operation it took 32”R and #6 turnouts. #5 turnouts work in some track arrangements.
