I'd been looking for a second set of 700c disc wheels (135mm) for a while now for my Norco Threshold. Found a set that came from a Giant Seek. It's a 700c, 6-bolt disc with 135mm dropout. Am I correct in assuming that these wheels should fit my Norco from the get-go without any issues? I don't have a lot of experience with disc brakes.

Thanks in advance.

Should be a drop in but you might need to micro adjust the brake calipers and rear derailler due to small (mm) offsets between wheelsets. Not a big deal if you know what you are doing. If not its a good time to learn how to do these. YouTube these subjects and go for it. Come back here and ask questions if you have any. They are very helpful here if you are willing to do the work yourself.

I'm okay with adjusting the calipers and RD. Just want to make sure the wheels are, like you said, a drop in.

Yes if your norco is QR