Question about non followers

Mostly when a post is good and get big engagement from the followers (since they are first one that see post) , then post can start expanding in terms of reach (explorepage,hashtags,dm sharing…) , after some hours post start being seen by non followers , since most of them that see the post are already well choosen by ig algorithm , is there pretty much a certitude that high % can engage with post ? , and if not can it impact overall reach of account as much as ‘followers’ if they dont engage ?

because it will be weird that ig algorithm with as much precision… will show to many that will not engage with the content .