i think in general it would be very difficult for them to do just as well as they do here, simply because fighting in a ring makes it much harder to take guys down, in the UFC the cage really helps the TD...but in the ring a TD is more based on skill than knowing how to use the cage
a ring demands a more technical fight and while i still think most elite fighters would do just as well, some of the lower tier guys would really have a tough time because even though they are really strong their technique isnt really that good and the ring would just make it a lot more difficult, especially for GnP since you can still pull out a sub close to the ropse, is easier for bjj guys in the ring, the cage really affects their bjj game
the reason im saying this is because most of the UFC guys are wrestlers or have ok striking but like to GnP...
in other words, tough to say, elite fighters yes, they would do well either way, thats why they are elite, but fighters in general? would have a tough time since your technique becomes a lot more important than sheer strength and good wrestling