Bummer, can you return the boxes?
I am a lowly beginner on LibreELEC, my understanding is that LibreELEC will run well on 1GB RAM and performance on a good quality SDCard performance should also be good, maybe no need to burn to Nand and lose Android.
This post indicates that you may notice little or no performance difference between quality SDCard and Nand [8.1.8] LibreELEC 8.2 for S905/S905X
Also there is a post on this forum showing how you can run LibreELEC from SDCard but store your runtime files in RAM
Good luck whatever happens
Yes I surely can return the boxes but seems a real pain to return it : contact support, delay for shipping, ... (you know, as most of these chinese sellers). I will try to find a partial refund to prevent all of this. In fact I've bought this box to make a multimedia center (plug the audio out to play YouTube video clips on a audio system) for my parents so I surely think that they never need more than 1 GB, but it's just that they sell this as 3 GB box.
But I prefer to install it on the NAND, it's not because of performance difference, it's because if there is a problem with the SD card it will boot on Android and it's difficult to explain them with distance how to boot on SD card (the toothpick method). LE on NAND seems the best KISS method. As they don't need Android (and I made a backup with TWRP) I don't think it's a great loss. It will just became a 32GB box with 31.5 GB free space