Hey @beautifulwithbrains26! It is possible to trigger rules32 based on being added to a particular sequence. As a result, if you manually add subscribers to a sequence via a bulk action36, and you have a rule (or multiple rules) that are triggered by being added to that sequence, then that bulk action will trigger those rule(s).
The same applies for importing into things like particular tags, forms, etc. — if a visual automation32 or automation rule32 are triggered by them (i.e. a particular tag/form/etc.) and you import subscriber into them, then that subscriber will enter into those automation(s).
That said, if you simply create a brand new sequence and don't have any automations associated with it, then adding subscribers to that sequence shouldn't affect anything else :)