There's already a handy option in MassPlanner that you'll be able to do this with.
Go to: Settings > Social Platforms > Instagram
You'll see a checkbox for: 'Enable different users/posts across all accounts.'
Then a few checkboxes down, you'll see: 'Enable different users/posts across instagram accounts with same tag name.'
The tooltip for this option says: Enable this option if you want MassPlanner to follow/like/comment/repost/contact different users/posts across accounts with the same tag name instead of all accounts. This option works only if the 'Enable different users/posts options are enabled.
So essentially, you can give one set of accounts the tag 'CampaignA' and another set of accounts the tag 'CampaignB' then MP will only follow different users on accounts with the same tags, but it could potentially follow the same users for accounts across different tags.
Hope that helps!