Interaction of the apps contacts, files, polls and circles

I would like to understand the interaction of the #apps:contacts, #apps:files, #apps:polls and #apps:circles better. I can structure my personal contacts (not necessarily Nextcloud users) by adding a group to each contact. So some of my contacts are belonging to a group, called “team”. I can use this group like a mailinglist and add it as a mailaddress to a certain mail which is sent to each member of “team”.

I cannot send shares to the same team and I cannot send invitations to polls by using the group. This can be done only if I create a circle with the same members like the group. It is a workaround which gives me the feature but I am not so happy about it, because I have to use circles and groups with the same members.
Is somebody in the forum, who can explain me the philosophy behind or is there a chance to bring this together, somehow?
Any hint is appreciated!