Welcome to the forums, and congratulations on your purchases!
I have no doubt you'll
love the KP. As for the the Tair-3S, it's a very fine 300mm lens. You'll want to work in live view mode to ensure accurate focus, and the very simple focusing mechanism can feel a little rough depending on the condition of the toothed focusing rack. It's worth getting a thread adapter too so you can mount the lens on a tripod if required.
As a collector of Soviet lenses, I implore you to leave the aperture mechanism electronic link cable in place rather than chopping it off, just in case you should ever sell it. You won't need that cable for use with your camera, but it's really best to keep the lens in original condition
Looking forward to your involvement here