If the use of a .308 is primarily for deer hunting, the "need" aspect of a scope has to do with typical distances at which Bambi is likely to be shot.
I know from experience that 3X is adequate for Bambi at 350 yards. My 3x9 happened to be set on 3X and Bambi showed late in the afternoon of the last day of the season. I didn't waste time worrying about scope adjustments.
My first '06 wore a Weaver K2.5, which was good enough for jackrabbits to 200 yards.
My father hunted all over wide-open parts of Texas with 4X and 6X scopes.
IOW, nothing at all wrong with a variable, but that's more a proof of one's billfold than meeting any real need. I happen to like 3x9x40, but it spends more time on 3X than on 9X. The latter is good for sight-in and for load testing, mostly.
Brands? I dunno. I haven't bought a new scope since 1997.
Low mounts are usually plenty good for a 40mm objective. The lower the better, since you usually get a better cheek weld with them.