The specific pack you choose is less important than how you utilize it when it comes to time and efficiency.
I really like the Kifaru 357 Mag but I ripped mine and switched to my Exo K4 and it worked very well.
The pack just needs enough room for your shooting gear, snacks, water, and rain gear. Then you need to have a system that allows you to remove the tripod and shooting bag as fast as possible.
I place my tripod running up the center of the pack (bottom in the Exo rifle carrier) with the sandbag laid over it and one strap securing them both. I do the same thing hunting. Walk up to the stage, drop the rifle on the bipod, drop the pack, and unclip one buckle. Very fast, and you have everything you need.