I'd never keep bucks and does together only put them together to breed
I have done both for many years, kept singly or in pairs, buck/buck, doe/doe, buck/doe.
It totally depends upon the rabbits - some MUST be kept on their own - but I find the health of a pair is better than single because they clean each other in hard to reach places, like ears. And a buck doe pair keeps moving as he presses his suit and she evades, and so they get enough exercise for optimal gut health.
Large cages are a must for pairs though, with many levels to jump up and around, and constant vigilance for the tell tail tufts of fluff that might signal fighting has started.
I like to keep a nest box in with the doe all the time and the buck live with the doe for 3 weeks. He then goes in with the second doe for 3 weeks, and then in with the third doe for 3 weeks. Then start over or he has some time off in his own cage. Sadly I only have room for two sets of four right now instead of my usual "You can't have too many rabbits!"
This pair though had been through the wringer and I totally thought she was sterile. I have never EVER had any dwarf rabbit take longer than 6 months to produce her first litter and Peggy is coming up on a solid year. They were only kept on for the manure they make as they are bog-standard dwarfs, unfriendly, and stand offish.
All four kits doing great, the new cage wire is here, Boris and Natasha are in the upper-level cages, an extension on Fifi's cage has been made and installed, still waiting on the wood but the roof panels are here for the lean-to, and the rat-proof shed is built and feed/hay can now live in it instead of in the loo.
It is starting to look like home now.