epix 2 screen viewing with polarized sunglasses

doesn't matter about that - its depends on whether the watch screen is polarized and if so how that polarization is done as this can can cause the issue, not whether its AMOLED/LED which doesn't make a difference. 

Had a sony phone which had bars, so when in vertical mode it was fine, but putting it in landscape the screen was black as the polarization of the phone and glasses was eliminating all light.

You can see similar effects on car windows etc https://www.revantoptics.com/blogs/the-lens/why-youre-seeing-rainbows-in-car-windows#:~:text=So%2C%20if%20light%20is%20already,window%20only%20partially%20polarizes%20light.

We are lucky because OLED screens are often covered with stressed glass that is thin, yet relatively strong. Stressed glass has molecules predominantly spaced further in one direction than the other directions. Such a material is called anisotropic.

Anisotropic materials usually will be active optically, in the sense that different polarization directions will propagate at slightly different velocities through the glass. Another description of this phenomenon is “stress-induced birefringence”.

So we are lucky.