I think you pulled it just a hair too early. Try going to 195 -200 next time. The extra temp will help melt the remaining fat. You can even go to 205. I never have a problem with greasiness, although I like the extra fat on the fat cap and I always incorporate it. As you noted, butts can have different levels of fat, so the other butts that you've done to 185 - 190 might have just happened to have less fat. You won't mess it up by going to 200 and the extra time and temp will help render the rest of the fat. Even 205 won't "overcook" it.
You can also remove the fat cap as it will simply sort of slide off, but to me, that gelatinized fat adds to the succulent nature of pulled pork. To me, it doesn't add "greasiness" but flavor.
It's amazing what 5 degrees difference can make. I've pulled at 185 before and it usually means that it doesn't pull as well and leaves more noticable unrendered fat. When I go to at least 195, I never have a problem and rarely have any internal fat to throw away.