Noob optics question

Noob optics question

So Im looking to outfit my new ar15. (See previous noob bayonet question) and I'm wondering what the best optics would be for it. My plan was a variable scope to 12x or so... but heres my real question: i greq up shooting a .270 win during deer season, but now im buying an ar15 for home defense, shtf, range fun, and doing it with some flair... hence, the bayonet. It seems by my google and chatgpt research that the maximum effective range of an ar15 is 500 yds or so. I was thinking i wanted to learn how to hit 800 yards but realistically, i might hit a target at that distance but would only go ding not clang. Its probably going to be my only rifle, so i want it jack of all trades. Im not gonna be kicking in doors ot anything like that... What do you guys think?