Specifically on the Ukrainian border they have something like 4 mechanized brigades in the first echelong, and maybe another 6 mech brigades in the second echelong, 100 km back from the border. On top of this there should be a battalion of airborne guys (with their helos, including attack helos), and lots of Spetsnaz (special forces) running around, the latter very likely already inside the Ukraine. All units should be in full combat readiness, and at a peak level of training: a mix of professional soldiers and conscripts at the tail end of their service time. This is a very sizeable force!

They reportedly have also been setting up supply lines. Therefore one might expect them to be ready for a Blitzkrieg-like incursion. But they don't need to do that necessarily.

A society committed to the notion that government is always bad will have bad government. And it doesn't have to be that way. — Paul Krugman