We know that Daemons' bodies are physical representations of a warp entity - we also know that the Chaos Gods create these Daemons from their own essence. Therefore, it should theoretically stand to reason that a Chaos God could have a physical body in the material universe.
However, it's worth bearing in mind that:
1) it still wouldn't really be *them*, in the way that a Daemon's body isn't the actual Daemon either, and their essence would return to the warp again if killed;
2) they would be severely weakened compared to their original form, as this is the case for all other Daemons;
3) the amount of effort required to bring the Chaos God over would be absolutely phenomenal, certainly beyond the abilities of the Gods themselves even combined, when you consider how much energy they have to expend just to get a rift open. So practically, it's not going to happen, unless the galaxy is already severely broken.
Basically are the gods actual Daemons or just a name of a particular cult/ideal/imaginary entity that has little Daemon minions?
You've nearly got it, but you're thinking about it the wrong way round. Daemons are miniature Chaos Gods.