Not Nikojiro, but here you go for the view angles and brightness :
So yeah, my pix are a bit blurry, but you get the idea : view angles are excellent and yes you can play outisde.
The only downside is that apparently, you cant flash a clean version of retroFW... Tried yesterday multiple SD card, multiple version of retroFW, and had no luck at all. I think its linked to the IPS screen, because handheld boot to a black screen. They might have done some modifications to the firmware.
Anyway, you cant still manage the main SD card (delete the MP3, MP4, roms that come with the handheld for example...) and upgrade the emulators (like Gambatte).
Code behind battery is : RG_300_V1.3 - 2019.6.3