Just my opinion in case of term engine brake. The presence of an engine brake has its advantages and disadvantages.
I've have been ran with an 4t supermoto with installed rekluse auto clutch. I would say that this is something like hybrid version between 4t and 2t.
At deep corners I definitely liked this feeling when nothing keep bike to move ahead, and bike really felt like 2t. At such moments I was a bit faster than really fast riders in front of me. But, after long speed lane on next deep turn lack of engine brake is really noticeable because it results that I had to start braking earlier, because brakes are only tool with which you can cut speed. Finally my conclusion would be about 60/40 between to have engine braking ability or haven't it.
If you comparing 4t with an 2t, then 2t don't have engine braking force at all, but 2t has brilliant advantage as less weight.
Through what to operate with an engine brake , slipper or regular clutch, that’s the next question. They both ensure enough engine braking force. Some guys like regular , some slipper. For example one local very fast TM rider said that he is riding with an regular clutch only. To my question, why, he said "I can do quicker start". So, it depends on.....