what works for me
Though the red dot and all its guises is still quite the rage for an AR pattern rifle, I prefer a low power, variable like 1-4x, or 1.5-5x size, with a standard duplex reticle. Additionally, though 30mm tubes are all the in thing as well, I like a 1" tube, as they are generally a bit more compact and lighter.
Let me add right now that you not need concern yourself with the front sight tower on your rifle. Simple mount your conventional scope with one of the various ring sets or mounts that raise the scope off the rail a bit. An example of this mount is the Burris PEPR mount, or the Nikon (paired) P-series rings. Additionally, if your scope is tidy enough (another reason for 1" tubes) you can mount a simple BUIS rear under the ocular (rear) bell. In the odd event your tidy low powered variable fails, you can remove it with either the quick detach system for your base, or in the case of the P-series, with a hex key. I keep the correct hex key taped to my rifle. You may see a wee bit of the sight tower in your field of view on the lowest power setting of the scope, but not enough to distract or disturb aim. On the top end, the tower will likely not be visible at all.
A dot is very fast at close range, but I feel I do not give up much speed with a low power conventional scope. As I am not doing entries in dim light, the extra speed and visibility of a dot really holds little advantage for me. The precision offered with 4x or 5x at ranges beyond 100 yds on smaller targets is a decided plus over dots. Yes, I can hit larger targets with a dot at 100 yds, and beyond, but on a smaller target, say a varmints noggin or a coke can, the magnification offered on a variable is attractive.
Finally, let me mention cost. I can get a perfectly satisfactory, tough as nails low powered variable for $225 or so, and it will not need batteries, ever. I do not believe I can get a dot of similar durability for that price. And it will need batteries, some day.