First of all, Megamod contains CC journey and a whole bunch of other things. You need to know that some of the other mods have been tweaked so that they all work together. For instance, the flax problem is solved if the only mod you use is megamod, but as soon as you start adding other mods that use flax, you will have problems again.
Any mod that just offers housing is compatible with CC, as long as it uses the same materials to construct those houses. Off the top of my head, I think Discrepency is the only modder who has some houses and other buildings that require unique inputs. His older housing mods use vanilla inputs, but the later ones require things that only his buildings can produce.
Then there are some instances where mods work together, but have different inputs. For example, bakeries have been made by Blackliquid, Kid, Discrepency, and RK. Maybe others I'm not remembering. Each of these has different inputs and outputs. I don't find that to be a problem, in fact I think it adds verisimilitude, since IRL you would find different things for sale, made with different recipes, at different bakeries. Other examples of this are the various smokers, food dryers, dairies, and apiaries. You can mix and match these.
Then you have some weirdnesses with fuel. There's firewood, of course, but also a whole bunch of other types of fuel, used in various product chains. These are not necessarily compatible. It won't crash your game, you'll just have a building pumping out something that no other building can use. The solution is to tear the building down and trade away the junk resource, and build one that produces a product you can actually use.
I'm sure there's more, but that's all I can think of off the top of my head.
