Enjambres; In the lab a varroa can live 5.5 days away from the bees, I doubt they last that long under winter conditions in the bee yard. In summer they die rapidly because of dehydration.
Varroa is spread by drifting bees, robbing weak colonies and carrying home their mites, and beekeepers exchanging brood that has varroa in the capped cells. It would be possible to exchange a comb that had a varroa or two walking on the comb, but most will be on nurse bees and in capped brood.
Having colonies side by side in pairs will not be a factor in varroa infestations so you are not rushed to move your colonies.