Here is what I do:
- usernames are unique by default, too many similar usernames are there already, so I do not think IG is strict about it. I try to make it relevant to my offer, nothing else.
-name and bio: I write them for every new account. That's the reason why I'm bad at scaling this up, I get bored after few accounts

I started experimenting with avoiding bio altogether, just putting my CTA in name field. You are limited to 30 characters there, it is kinda hard to avoid similar names in same niche, but people say IG is not so strict with names like it is with bios. We'll see how it goes...
-profile image: at first I added different images for every account, now I just resize and rename one picture. MP also changes it before uploading, I guess it is good enough.
-proxies: when I don't know what's wrong, I blame it on proxies

I changed 3 different providers (1 max 2 acc/dedi) and I can't be sure about their quality.
-links: I create new prelander for every account.
-phone numbers: this is a problem for me. Using SIMs is huge pain in the ass, using Chinese numbers is easier, but risky.
-reports of users: no posting videos (if you gotta post), no posting at all reduces reports.