Silver skin for sure remove. That stuff will not render. I wouldn't worry too much about the other fat
I agree with Pappy.
I'm no expert, but for me a lot of fat is not a problem on butts.
For clarification, I do mean pork butts.
( Good one!
)
Just an idea about silverskin and fat:
The fat will become less of a problem if you ramp up your cook temps to 275F - after you have hit the "stall". The reason is that the slightly higher temp. will help to melt away more of the fat. The meat will not suffer. It will not be dry. ( In fact I have often cranked up the temp. to 350F for a few hours to "set the bark" - then back down the temp to finish the pork.)
About the silverskin: -
time can help - and even make it go away - as in dissolve - when using sous vide. Not that you would do that to a pork butt
When I have cooked various roasts that will have silverskin between muscle groups using Sous Vide - then finish them on the grill ( and often pre-cold smoke them before the sous vide part...really nice mellow smoke profile is easily achieved ) the time at lower temps really allows the silverskin to virtually melt. It either disappears - or almost disappears - situation dependent.