[wrxtasy]

Ordered Tanix TX92 - 3GB RAM and 64 GB ROM, going to order external storage for Librelec.
What is recommenced USB stick or micro sd card? And what size?

 Really bold move...
Tanix has a really bad reputation regarding their players...

Is that so? Seller hasn't shipped my order yet, I can still cancel it.
Which else box would you suggest for 4k HDR10 kodi movie movie playback?

At the cheap end of the market they are all going to be virtually the same. It is cheap hardware after all.
You could ask a whole bunch of users of cheap Android products and they will also tell you to stay away from certain brands as well.

The branded stuff we talk about on the Kodi forums, usually has higher spec RAM, eMMC, WiFi ...
I'm talking about ARM based products like Raspberry, NVIDIA, MINIX, ODROID, Vero, Apple etc etc.

Extra care is usually taken to source higher quality internal components.

ODROID for example even cancel projects or halt hardware production if they cannot source the correct RAM and eMMC at decent prices. It's all about quality control.

At the dirt cheap Android end of the market, you basically end up with components that are the cheapest available for that production cycle.
And often the exact same named boxes will come with different spec - RAM, eMMC and WiFi chips. It's all a bit of a lottery.
Usually the S912 devices at least seem to have common AC WiFi and a bunch of them have GigaE.