[wrxtasy]

 

Intel hardware will give you better Software upscaling picture output quality of 480/720p >>> 1080p content vs LE running on AMLogic hardware.
You cannot use Lanczos3-optimised upscaling for example on AMLogic hardware. 

 Does it have problems also with bicubic upscaling or such? I hope that my 480p documentaries will not look all blocky on 1080p TV, because of nearest-neighbor filtering

You only get CPU Software upscaling options like Bilinear and Nearest Neighbour when Software decoding video content with Kodi.
By default AMLogic LibreELEC does NOT software decode.
It uses Hardware decoding and Hardware upscaling for everything OR...
Resolution switches 1080p <<-->> 4K to allow a 4K TV to do 1080p >> 4K picture upscaling.

AMLogic Hardware upscaling does not look blocky, it's just not quite as sharp looking vs what high quality software upscaling will do to SD content.
Nothing will fix low bitrate SD streams.

The only device with my custom version of LE Krypton I have doing 720/1080p <<-->> 4K auto resolution switching is the ODROID C2.
LE on an AMLogic S912 cannot even switch to a 720p video output mode. Lowest is 1080p.

Forget about all those high quality LE Intel CPU Software Kodi picture upscaling options like Bicubic, Lanczos3 etc that give you sharper SD quality picture outputs.
The best you can use is Nearest Neighbour when using LE AMLogic Software decoding for SD content, even that looks find for 720x576i OTA TV.