Windows version: Windows 10 or higher.
Processor: Better have a Core i3 or stronger (in weak processors, such as Atom, you might have low performance and no text acceleration).
Memory: 8GB RAM (more is better, if possible).
Storage: 32GB or more.

Can be TV box, dongle, tablet, desktop or laptop.
Android version: Lollipop (5.1) or higher.
Memory: 2GB RAM or higher
Storage: 16 GB or more. In case you have huge videos (total bigger than 2GB), better have 16GB storage.
Screen rotation: In case you require to support screen rotation (portrait mode), you need to confirm that you Android hardware/firmware supports it and that you can either rotate the whole operating system or allow an app to rotate the screen (these are 2 options which can be found in the Android settings, in case you have screen rotation).
Multiple videos: In case you require to display more than one video on the same screen (i.e. 2 or 3 video widgets on the same composed creative), you will need the firmware to support it. It is possible to find different firmwares for the very same device, while one firmware supports only 1 video at a time and another supports even 3 videos in parallel. 
GPU: Mali-400 works ok, but Mali-450 is a little buggy with whatever it has to do with videos transitions (when you transit into or from a video), but can be handled by proper fine tuning the video transition settings.