Device count matters far less than what those devices are doing. You, your VA and your team can all stay logged in without causing problems.
What does cause problems is more than one party running the same activity we’re running: bulk following, unfollowing or rapid liking. Those totals stack up on Instagram’s side and make temporary blocks much more likely. Scheduling tools connected through Instagram’s official login are completely fine.
Worth doing occasionally: check Settings → Accounts Center → Password and security → Where you’re logged in. If you spot a session you don’t recognize, log it out and change your password, then send us the new password and a fresh backup code.