Don't know about "clumping", but both drosera capensis and binata have grown new growth points next to existing ones. This eventually results in multiple plants, of course, but it isn't very clump like to my eye.
Aliciae/curviscapa have done more plantlets over time for me.
But what comes to my mind as "clumping" happens most with my drosera andromeda and drosera adelae. The andromeda has entire plants growing under larger and older leaves at times that I start to see only because they have got too big to remain hidden. Last time I repotted the andromeda, some of the leaves were almost vertical, because there was no space for "rosette". They are also super easy to propagate without much risk. Just dig into the media and pull up a root closer to the surface and it will start forming plantlets. This happened for me accidentally (I'm not trying to propagate right now because no space, so I'd like bigger plants instead...) But they both are picky about humidity and don't like dry conditions so much. Adelae is worse than the andromeda. If your conditions are dry, I wouldn't be surprised to see the plant itself dry out, let alone forming clumps - so this may be a drawback.
Edit: Prolifera also, though I tend to kill it from too much light. Advantage with andromeda and adelae is that they are quite a bit bigger than the likes of aliciae. So they can take over quite some space from the sheer size of each plant very fast in addition to their natural inclination to take over the world.
Another plant worth considering is drosera burmanii. It is short lived and won't branch from roots or even strike cuttings at all, but a a single flowering burmanii has the capacity to cover a considerable area with burmanii, because they flower within months of germination, are self fertile, germinate fast and..... well... the result can be a carpet of burmanii in neglected pots (don't ask how I know or what happened to a batch of nepenthes I was trying to germinate)