The Blue Force Gear Vickers sling and the Ferro Concepts Slickster are a couple of my favorites. I personally wouldn’t run offset irons with an ACOG, that’s just me though, and just slap on some flip ups since with the ACOG you don’t have to worry about batteries dying, just the glass breaking. When I was in the Army all of our rifles with ACOGs had flip up rears (couldn’t use them with ACOG installed) so that if anything happened to it you could just take it off and still be affective. Since you’re planning on getting the optic down the road, it might be wiser to have your irons on top first while you wait. That’s just my opinion, I’m just some guy on the Internet. Best of luck man!

Seconded on the Vickers sling -- I have the padded one on my DMR type, and it's been great. I tried out the adjustable magpul one, which is just ok -- to me it doesn't justify the cost savings, which is minimal, especially to the unpadded Vickers. I don't have experience with the Ferro Slickster.

I personally like offset irons for a scope, but you should 100% put some irons on, and practice with them. For offset irons, Dueck Defense and KAC fold downs are both nice (but a bit pricey). The advantage is they're much faster to transition (Even the KAC ones are, compared to a throw lever), but they stick out a little and can limit space for a light. KAC sticks out less, but is slower to transition, and I had to mount the rear sight a little forward because it interfered with the ambi charging handle. Duecks will take standard A2 posts, the KAC ones do not, so if you want to swap out the post be aware. Otherwise, Magpul does good with their pro flip up sights, or some other reputable Made in America company that does sights -- I'm less familiar with the straight irons.

If you are talking for an AR they make flip up front and rear sites. Magpul and many others make them. If you have a front post fixed site already just get a rear flip up