Long ago I came to the realization I was never going to have the space (1200 sq feet, geez) for a large layout of any kind. That being said I have an eight ft by 2 ft O scale switching layout built on 2 inch pink foam. Older atlas turnouts, atlas flex track, straight DC, two atlas locomotives, a SW and a plymouth plus a bakers dozen weaver cars. Easily brought out for some fun and easily stored under the 3 rail layout. I like shelf layouts because they can be completed quickly and offer some operational opportunities without breaking the bank. My other shelf layout is a 1 x 7 ft HO version of the Gum Stump.
Over 20 years ago here in central NJ there was a round robin group of 2 railers, I'm not sure if any of the layouts exist to this day but they provided they inspiration to try something. There is one club in North Jersey and one in South Jersey.