It's a huge myth that you can only use 4-5 accounts per domain (especially with shops). Look at everyone in the fitness industry promoting the same supplement or apparel shop and spamming their coupon affiliate code. Instagram knows there are some scenarios where plenty of people use the same domain.
Maybe with CPA it's a good idea to use less, but if your landers are good, you could bypass it. I've done 10+ before too with CPA, but you'll need everything else up to code (aged accounts, non-shady website, proper warm-ups, etc).
You can use 20+ accounts per domain as long as Instagram doesn't hate your website. If your website isn't spammy or covered with affiliate links, Instagram usually won't have a problem with it. Just don't do anything crazy with automation (keep it under 700 follows daily).
Good luck!
Source: personal experience, currently have several set-ups with more than 15+ accounts per domain