I've had good luck with the CDNN cheap $20 red dots, although I've had to add a drop of LocTite to the battery compartment screws on most of them, after that they've held up well, I've a 30mm on a .308 and a 1" on a .44Mag revolver so they seem to hold up well after you fix the screws coming loose issue. Battery life could be better but they use the cheap computer coin cell lithium batteries (cheap if you buy them in 10-packs on-line)
Co-witness is very unlikey unless like the EOTech and the AR15 the sight was designed for the gun in question. Be happy if it mounts so you can use the irons through the red dot tube or window.
I recommend starting with a cheap red dot as they are different and not everyone will like them. You have to look through the dot and focus on the target, if you focus on the dot you will swear the sights "don't hold zero". Since you are probably used to focusing on the front sight or a scope reticle, it takes some getting used to when shooting a red dot the first few times. Also a lot of people end up not liking the accuracy for speed of acquisition trade-off inherent with red dots.
--wally.