OK, first issue.
If your rifle has a fixed front sight base (the standard sight on AR's, which I believe it will)....no problem. A BUIS should work perfectly fine with either, provided that you do not have a riser or something like that on your flattop. This would raise the height of a rear BUIS and would make zeroing almost impossible unless your rear sight is a special low model...but that is a whole other mess. If your flattop is bare, or just the flattop with nothing on it, you're OK. So the rifle as is, with a BUIS is good to go.
I recommend the Troy BUIS.
Second Issue:
"interfere" is kind of subjective. There are many ways people mount optics to a rifle. It also depends on what optic you are trying to mount.
If you mount an aimpoint for example, then the front sight base will certainly get in the way of your field of view. How much is the question. If you look at the sticky's at the top of this forum, there is a diagram of how this looks through a sight.
Seeing the FSB through the optic is a GOOD thing for most people (so long as the optic is not magnified). This is called co-witnessing, and its purpose is to allow you to deploy or use your back up iron sights in the event your optic fails. There are 2 styles of co-witnessing. There is "absolute" or "center" co-witness. This is where your iron-sights line up dead center in the optics view. Then there is "lower 1/3" co-witness, this is where the iron-sights line up in the lower one-third of your optics view.
Obviously, the lower 1/3 style of co-witness keeps the front sight post and irons out of the way as much as possible to preserve the most field of view.
So, if you decide you want co-witnessing, you will have to pick a mount for your optic that achieves the desired co-witness. EOtechs are the same, they require a riser mount to co-witness in the lower 1/3. Aimpoints have a variety of mounts, and you'll have to find out how where each one mounts in height.
Now, if you don't want to see any iron sights in your field of view, then you will need to have both FLIP UP iron sights for the front and rear. Rear is no problem, as many of them come this way, and you just mount it to your flattop. The front ones are different. That will require you to remove the standard front sight base (which is also the gas block) and replace it with a gas block/flip up front sight combination base. The other option, would be to replace the FSB, and replace it with a gasblock that has picatinny railing on the top and possibly the sides (for other purposes) then you can add a detachable flip up front sight to this.
My advice. Forget messing with the front sight. Leave it be. In a scenario where you will have to deploy iron sights in the event your optic fails will be one where TIME is not on your side, therefore....having to deploy 2 flip ups vs. just the rear is a big increase in time. Rear BUIS that flip up are very fast. Much quicker to do that and stay in a shooting stance. Flipping up the front will take you out of your ready position.
Also, if you use the Aimpoint, then you can use the Aimpoint as a giant ghost ring with the front sight if you do not have time to even engage the rear flip up.
I prefer the rear flip up BUIS with a lower 1/3 co-witnessing mount for my optic. This is the best of all worlds. No front sight to mess with. The sights are reasonably "out of the way" of my field of view, and I still maintain co-witnessing capabilities. Oh, and the price is right. Front flip ups will add quite a bit to the budget, enough so that you can easily pay for a mount that does lower 1/3.
Beyond that, it depends on the individual optic you will choose. That will dictate which mount you want for what type of co-witness.
ALL of this is assuming the optic is not magnified. If you get an ACOG, or some other scope-type magnified optic, then the whole BUIS system must be thought out differently. For example, the magnified optic will probably need a quick detach mount so that it can be removed so that irons can work.......etc...