balbes150 Please refrain from speaking about a device you don't have hands on experience with.
I can't compare it to the RK3399, as I don't have a box based on one of them.
I have a SBC based on another Rockchip, and the last time I tested it, it was pretty useless as a media player in all regards.
H264 video stuttered, HEVC video would lock up after 10 seconds of playback, no HDR support, etc.
The N2 doesn't heat up to 70C, the maximum temperature I've seen on mine was when I was playing H264 4K content with SW decoding (all cores at 100%), and it maxed out at about 42C, so if you have no idea what you're talking about, just don't, it doesn't sound good.
Regarding it not being good value for money, that also depends. Cheap Chinese boxes are often shipped with cheap, bad or fake hardware. Hardware which you can never get proper drivers for or get to work reliably (or at all). With HK, everything provided in the box just works, and it works well. Everything is high quality, and quality is not cheap, so there's a premium. You still don't know how much S922X boxes are going to cost, and keep in mind that some higher quality Chinese S912 boxes sold for well over $100.
I still don't understand why you fixate on the Kernel version, how old it is, or what GPU drivers it has. As long as it works well and fast, and it does work well, and it's also very fast, I personally don't care what version of kernel it is running on.
LE pushes towards Mainline kernel support, I can understand why, LE has to cover multiple different platforms, so it makes sense for you.
Not being able to run mainline LE on it doesn't make it a bad device or a bad buy.