I use both a ring swivel or a loop knot tied to the swivel, if is simply a case of which I grab when I grab a combi rig out the rig bin.
I only use a ring swivel, with the rig tied to the ring, for combi-links. I am happy to tie a loop knot on combi rigs as well.
For braid and coated braid, I think that the braid is supple enough to allow enough movement, but with combi-rigs I want a loop or ring for the added movement.
If on very rare occasions I use a silt or chod rig, then obviously the ring end of the swivel is on the tubing I use and the rig on the other.
I don't often get tangles, and on many occasions I fish without tubing. A run ring sliding up and down the mainline, then two rubber beads protecting the mainline to swivel knot and to stop the run ring sliding over the swivel, or run ring on tubing, and the tubing pushed into a buffer bead.
It also helps that I cast out with PVA bags, stringers or mesh every cast, that prevents most tangles, but even without it, I am sure my rigs are tangle free.
I always tie a fresh rig onto the mainline, I do not use quick links, I don't like them, I have seen too many lost fish down to them, and I have lost fish myself down to them, and I don't do stick mixes as such. I attach a PVA mesh bag by the simple means of an overhand knot around the mainline or tubing above the run ring, and then the hook point pushed through the mesh.