The "rules" of what are C&V are over at the Classic Rendevous (CR) site - t least that's where someone's posted them. Here, it's whatever you want them to be. As I've stated before, the CR site is like a wine bar, I call this forum the dive bar. It's really a forum for people who like and appreciate older bikes, with a somewhat fluid definition. You can post threads of bikes that aren't really C&V on occasion without getting much grief.
I went to Bob Freeman's annual (pre-covid)
show and ride a few years ago, one gentleman had an e-bike. But he was 80 years old and wanted to participate, and I was told he was big in classic bikes BITD. Who's going to kick him out?
As for organizing C&V rides, people on this forum have been doing that for a long time. There are just a few that are "regular" rides, the Pasadena one seems to be the one I keep seeing. In the past few years I've done a Ride, Wrench and Grill a couple of times with good turnout, and a couple of North Trask rides (~Portland to Tillamook over forestry roads), all of them with a dozen plus riders, but never enforced any rules on C&V bona fides.
Want to put something together like a Bay Area Cino? I'd bet something that took place Marin/Napa/Sonoma area would be a hit. The Bay Area is a lot easier to find flights into from far and wide than Kalispell or San Luis Obispo, and would automatically draw from the Bay Area easily, PNW with little difficulty, even SoCal - all are within 1-2 days driving time as well. In addition, the North Bay has wonderful weather almost year round, so it could be scheduled at a time when other places in the country are too hot, too cold, or too wet. It would be a lot of work if you're planning on charging, food stops, county permissions, etc., but a smaller scale, informal, self-supported ride would be easy to organize.
Hmm, I know a guy in Monte Rio...