Those formations around Sumy and Kharkiv are probably to keep Ukrainians in check there. I doubt that the Russians will truly try to encircle them or take them. The Russians will go very cautiously and deliberately around there if and when they make advances. No more foolish Zerg Rushes well ahead of logistics and supplies and without proper and/or overwhelming air support.The latest Russian movements and reinforcements suggest that the Russians are not just focusing on the Donbas. Large armored concentrations are now entering Ukraine around Sumy and Kharkiv as well. This does make sense strategically, since the Russians can't leave the Kharkiv front too exposed, otherwise the Ukrainians might counter-attack along their vulnerable flanks in Luhansk. It seems what's changing is that the Russians are just deploying to the eastern front all along the former border with Ukraine. This makes it easier to resupply their armies and makes the Russian war effort much more focused and concentrated. Kyiv and Chernihiv were disasters from the start, so the Russians were right to get out of there. We'll see if they have better luck around Sumy and Kharkiv the second time around.
The Russians learned their lessons of the 1st Chechen War that they applied in the 2nd Chechen War after being chastened. The Kyiv- Chernihiv operation was a disaster because they had forgotten their humiliation of the 1st Chechen War and decided to throw away caution assuming or gambling that the Ukrainians would sue for peace the moment the Russians showed up at Kiev's doorstep. They never had remotely close to the number of personnel and equipment necessary to surround, yet alone take Kiev. Having been chastened by that failure, the Russians will act accordingly this time around.