Can't answer that question without knowing what you have.
The MBUS rear sight will be proper milspec height.
Commercial grade ARs like RRA, DPMS, Bushmaster, Oly and others do not have the milspec height front sight so they could have a zeroing problem, especially with a 100 yard zero.
Milspec style ARs like Colt, BCM, Daniel Defense, LMT, Spikes, Sionics, PSA and others shouldn't have issues.
What kind of optic are you thinking about?
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
You'll remember the quality of a gun long after you forget how much you paid for it.
US Army 1966-69, VFW Life Member, Retired Geek