Starting Sweden top tier, but I'm kinda undecided on what to grind first.

I'm confused cuz of the Cv9120-T being 12.0 and the Strv's being 12.7, the CV9120 being 12.0 sounds good in my head, but grinding the Strv's that are 12.7 sounds scary as the first time playing real top tier. What should I go for?