Grid

Timeline Changes but only 1 year back
Thriller/Mystery
Serial Killer on the loose
it will give you the vibes of what will happen next

Timeline Changes but communication through a Walkie Talkie
Thriller/Mystery
Serial Killer on the loose from the past
it will give you the vibes of what will happen next if the timeline changes

Timeline Changes from 1988 to 2017
Thriller/Mystery
Serial Killer on the loose from the past to catch in the future
it will give you the vibes of what will happen next if the timeline changes

Timeline Changes from 2018 to 1985
Thriller/Mystery
Serial Killer on the loose from the past to catch in the future
it will give you the vibes of what will happen next if the timeline changes

In both shows the leads are socially awkward outcasts. They also idolize their popular love interest.