Thumbnails that read at a glance
A thumbnail is usually seen at around 200 pixels wide, beside a dozen others. At that size only three things survive: one clear subject, a few large words and strong contrast. Serious horror channels tend to avoid cartoon arrows and shocked faces in favour of a dark image with a single, legible line of type.
The layouts here follow that approach: title left or right of the subject, a lower-third band, or a centred title over a darkened frame. A live preview at the size YouTube shows on a phone tells you whether the title is still readable before you export.