NONE of those..a good old plain Jane ho-hum 7mm Rem Mag will do everything and anything all those fly by nighters and hanging on by a threaders will do and more than likely more than most....it has stood the test of time without question...with no anxiety, added expense or worry !
I have shot the 284 in 22 and 23 and 24" barrel lengths and have settled on 23" as being the optimum for this caliber. With the 22" i lost between 40 and 60 FPS depending on bullet wt and the 24" only gained 20 to 40 FPS with the extra inch. My max velocity with with TSX bullets was 200 FPS than what I've been able to achieve in my two 7-08's. Per the formula I've developed based on bore diameter and case length, 22" is the optimum barrel length for the 7-08