I took some pictures to illustrate my findings:
From left to right: UE TripleFi 10 Pro tip, UE900 tip (gray), UE700 tip (clear), Auvio tip
UE TripleFi 10 Pro tip on KEF M200 nozzle, very wide bore, almost all holes on nozzle are unblocked
Auvio tip on KEF M200 nozzle, outermost holes semi-blocked
UE900 tip (gray) on KEF M200 nozzle, notice how the structure of the tip interferes with the outer most holes on the nozzle, which may or may not be why the treble is less smooth sounding to me (YMMV)
I have a bunch of other tips that work to varying degrees on these as well, but these third-party tips seem to be the ones that are most talked about here. For example, I've had success with a couple pairs of clear tips that now come with the HiFiMAN RE-400. The smaller pair of the two looks close to the stock tips in fit and appearance, and I think people with larger ear canals may benefit from the larger of the two pairs since it's pretty big and bulby all the way to the tip (with a very wide bore).
FWIW, the stock tips seem to have the widest bore of them all (very slightly larger than the TF10 ones).