I am in the process of building my first flat top rifle.  I need an "optics plan" to start working towards.  I see a variety of setups flip up BUIS vs non flip up.  High mount aimpoint vs eotech or OKO.  What about a fixed non lighted 3-4x?  I need to get the uper first obviously and then a BUIS.  What I need to know is what kinds of BUIS will work with what sight options?

I am interested in the CavArms A1 style apature, but it doesn't flip down.  Does that limit my future optics choices?  I see fixed BUIS' on rifles with scopes, how do people use the optics with the rear sight in the way?  What about the front sight? (I really want a normal front sight)

I need a good rear sight because this is being done on a budget, and it will be a while before I get the optic.  I don't think I will ever have the oprotunity to play with all the possible configs to see what I would really like so I really need some informed opinions heer.