I think concessions from the West would be better for Russia. But since they aren’t giving them any, Putin seemingly had to go in with his “peacekeeping force” or be called on his bluff.
I think Putin might plan to invade Ukraine to the point of making a land bridge to Crimea. Because I don’t see how Russia’s position has been improved with this move, even if Ukraine backs off from Donetsk and Luhansk completely.