Sarah brings good point. I thnik racey roadies can be pretty snooty about equipment, I am not sure why. Just my opinion. You will see all manner of bikes or trikes or velos or tandems or recumbents or heavens forbid, fixies on a brevet and nobody judges from my experience. Whether you sport 36 hole aluminum rims or the latest dimpled Zippy carbon wheels, nobody will even notice. The focus is more on the ride and the experience. An apt comparison might be long distance hiking versus a 10K runner.
I ride a recumbent nowadays. At a cafe break on a training ride, one roadie was looking at my recumbent asking a few questions and his buddy says, "What is wrong with you, why aren't you on a real bike??" The first rider was still asking questions and the other one blurts, I like your jersey. Where can I buy it. I said, you can't. You have to win it. He did not get it.....the first guy then says, "see, he IS a real cyclist" and the other rolls his eyes bigtime. Randos might geek out over your shiny brass bell but you won't find someone criticising over gear too often if ever.
Another obvious difference to general riding is distance. Randonneurs do 200k, 300k, 400km, 600km, or 1200km with a maximum overall time of 13.5 hrs, 20 hrs, 27 hrs, 40 hrs, and 90 hrs, generally IIRC. Most sleep once on a 600k. 400k is generally done straight thru. This is about 250 miles and is a very common distance. General racing riders would very rarely do a ride this long. Some Randos like to stop and have a nice lunch and nice dinner on a 600k. They will tend to ride together. Others like to get to the sleeping spot as early as possible to get as much sleep as possible, I know that is my way usually. I don't ride very fast or hard, I just keep stops to the bare minimum. This is like money in the bank or more properly, sleep that you can take. Almost everyone sleeps once or twice on a 1200k. I slept a ton on my last two 1200K grand randonnees. I did not sleep at all on one. Where and when to sleep is so variable that I think staying with friends on such a long 1200k is very hard.
I was feeling weak on a 600k in DC towards the end of the first day. Three strong well known randonneurs pulled up. I knew them but they did not know me other than just a fellow Rando. Obvious, I was suffering. Did they just pass me? No. "Get on our wheels". One young lady told me chicken jokes for like 2 hours. They never made me take a pull. Not once. I eventually recovered after a dinner rest at Mom and Pop sandwish shop. Is that unusual? On a New England 600K in nasty, pouring rain I was cold. One of the fastest Randos ever (Brad) pulls up and would not let me leave his wheel. He hauled my carcass from the middle of Massachusetts to the finish. My bike broke on a 300k qualifier for PBP. I was the lead rider by far. Every single and I mean every single rider either stopped to help or offered. There is a fellow in Florida that I have done several fast brevets with. We will often ride pretty slow for an hour chatting maybe letting food digest and one might say, "time to ride again?" and we will pick up the pace taking turns pulling. In my first PBP, I got dropped in the hills leading into Mortagne. I caught. There was an older Frenchman who came back and kept telling me in French to breath and increase my pedaling suppleless. He was the old school commander (one water bottle and one tubular strapped to seat with a Binda Extra) and looked after the young american. These types of differences are not so obvious but there is a world of difference.