Maneuverability doesn't matter in a straightforward BVR fight, but energy retention (the ability to efficiently turn speed into altitude and then back again) and engine power do. A fair BVR fight looks like jousting, with both aircraft going hot to fire and then going cold to defend the others' missile.
A good BVR aircraft should have decent energy retention and should be able to repeatedly speed into the engagement envelope and then swoop away.

Most BVR fights aren't fair, however. Usually they involve a couple of aircraft following straight headings, one party sees the other first, and blows them out of the sky before the target understands what's happening. In that context: stealth, AWACs, radar power, and other factors are more important than aerodynamics.