The main difference is that only -miş isn't used with a first person action. To understand this easier,  you should now that its other name is "duyulan(heard)  geçmiş zaman". So it sounds quite odd when you talk about your actions like you heard them from someone or learnt them from somewhere.

"Ben bu filmi on yıl önce seyretmişim." has a meaning like " they are saying that I have watched this movie but I don't remember that."

But "Ben bu filmi on yıl önce seyretmiştim" has almost same meaning with "seyrettim". So it should be used if you are well-aware of your action.

Other than that I think that other differences are story telling issues. Correct using make your expressions perfect but also there are many native speakers who dont use correctly.

I hope someone gives better explanation,  I just want to be sure that this question didn't remain completely unanswered.

You're welcome.