I don't have direct experience with where you are going but I have my share of hours on pacific northwest rivers and could offer some comments...
The Loop gear sounds great, you're clearly going to be well-equipped in the rod and reel department.
As far as lines:
By June it will be just as important that you can cover the water well, control the line speed and swing, and present properly for each pool a it is to get down vertically. By then there should be plenty of opportunity to fish away from the bottom and the additional flexibility provided by a sinktip system would get my vote.
I'd guess that you are targeting sockeye, summer steelhead, springer kings, trout, and ocean coho at that time. Summer steelhead, trout etc will move for a fly, the other species will require really slowing the presentation down except for the ocean coho which are going to be best pursued with a single hander and they like it strip-retrieved.
If your question is about Spey shooting heads or longer belly lines with a loop for tips, this could boil down to being a matter of preference for June fishing. I don't think you'll need to have the hi-density tip throwing difference of the shooting head that time of year.
Please feel free to elaborate on your upcoming adventure and I'm sure the replies from others will help you decide on a line choice.