I have a 921 with a SHO, and Bob's JP, so I'm running different props, BUT... I want optimum performance... Gotta have it! So...
I get every prop worked by Croxton right after I run it a short time. That way I know if it needs a little more tweaking than just a b&b.
I run T1-25 & 26. Had my 25 b&b'd and had my 26 down pitched to 25.3 with a little tip added. That's a sweet prop.
Having said that, I have a friend with your 721 set up, but with 8' blades. He runs a 25 Fury stock, but ALWAYS runs his Atlas up to 16-17, ALWAYS!
Dude drives the gel off that thing! It flies. He has said that a Croxton worked prop is better, but he gets a new boat every year or 2 so he stays stock.
Don't worry about taking that Atlas up some, you'll do way better than 75. just watch WP, as I'm sure you already know.
A 721 should be hitting at least 77, actually a bit more by yourself. You sound like you want the most that boat will put out, then I would get all props worked.
But only after you know what they need. When Croxton gave my 25.3 more tip, I got the perfect lift.
Sounds like you gotta have optimum performance like I do. I hit over 74 in my 921, occasionally 75+. So expect more from your 721.
I have the same problem you do tho...I carry 30 rod/reel combos and have EMPTY livewells too...go figure.
Stay safe!