Yep, but there's no roster or dues on the groups I ride with regularly. A couple of groups or clubs have club jerseys or t-shirts that most folks wear on those organized rides. Most of them have evening rides during the week to accommodate member schedules, and one or two daytime weekend rides.
One local group emphasizes fixies, probably due in part to the earned animus against rookie fixie riders in most groups. Multi-geared bikes are welcomed, but don't gripe about how the fixie riders ride. Usually there's no problem with experienced riders who can track stand without weaving all over the place, or don't endanger other folks with skids, etc. The problem is with incompetent fixie riders in large casual groups where many participants are barely competent cyclists.
There are a few more organized clubs, dues and rosters, etc., but I haven't joined. Most of the groups I ride with occasionally are just for special events, fund raisers, etc. I'll sometimes join their training rides but seldom ride the actual events. Unless it's a full century or longer with some roadside support, I'd rather ride on my own or with a couple of friends and work out stops along the route.
The roadie group I ride with morphed a bit over the past couplafew years but it seems to have settled into a groove that most participants find acceptable. For awhile it was one ride, no A or B, but as some longtime members aged and younger riders joined, it wasn't practical to expect everyone to hold an A or A- level pace.
So the fellow who started the club split it into A and B, with the B pace around 14-16 mph. Ride leaders are ad hoc, depending on who shows up. And the pace is adjusted accordingly -- especially summer rides the temp is still over 100, when it's closer to 14 mph tops.
The A group is often a free for all hammerfest, which is what some folks wanted. Nominally no drop but it never works out that way. Most regulars form up small co-ops of 2 or 3 friends to pull each other as the group splits, usually after a couple of climbs. My only concern about that group is without clear leadership and guidelines it's often sketchy, even dangerous depending on who shows up. Some guys are strong and fast but not safe in groups. They'd get a good
yelling-at by any of the serious local teams. I occasionally see the local pro team training on a nearby route and they're completely different -- tight, smooth, controlled and fast. They have a few participants who aren't active pros, because they ride with the same discipline and ability.