If the nozzles are level and you're getting head drags - you're bed is not perfectly level.
Solution: add a level bed. I use 3mm aluminium.

Also leave both heads in place and level once you've sorted the bed out. Otherwise the head you use gets worn down by rubbing on print (when it goes back over extruded parts of alayer to reach unextruded areas) and you go back to the uneven heads job again.

I fitted two new nozzlkes a while ago and had no height problems since.

But the most important issue is getting a perfectly level print bed.