Group creation limits will be enforced based on the number of groups you are currently an admin in. For example, if you are an admin in 5 groups, you will not be allowed to create a sixth group or become an admin in a sixth group.
Upload limits will be based on how many total posts you have uploaded to any group. For example, if you upload 1,000 photos to one group, you will not be able to upload another photo to any other album.
The limit on the number of members per group will be enforced based on the maximum number for any admin of the group. For example, if one admin of a group has a Pro plan and another admin has the Family plan, the number of allowed members for the group is the larger of 100 or 1,000, so 1,000 members will be allowed within the group.