For a varmint setup you really can’t go wrong with a 22-250, 25-06, or a 6.5 Creedmoor.
Personally, I like the 6.5. It’s a little slower, but more efficient and you’re pushing about twice the bullet, but still over 3,000 FPS with the right load. I guess for a dedicated varmint rig it doesn’t matter much, but 6.5 is much more versatile IMO and can be a do it all rifle in our region if you want it to be.
As for the scope, I’m happy with all 3 Vortex optics that I have. I set up a Ruger American 30-06 somewhat on the cheap. I spent the extra $70 for the Diamondback scope based on a couple recommendations. I can’t knock the Crossfire because I don’t have one, but I am very happy with the Diamondback.