You are correct - the VI10 Plus only comes with RemixOS (no Windows) and only has 32gb of storage... My guess is that your Hi10 Plus just has some bad RAM...|
If you go into the BIOS on my Hi10 Plus, the main screen shows "Total Memory 4096 MB (DDR3)" and under Chipset->North Bridge, it shows "Memory Slot0 4096 MB (DDR3)" as well (with Memory Slot2 being "Not Present").
My guess is that Chuwi either installed the wrong RAM chip or they used the right chip and some of the RAM on that chip is bad. Either way, only solution is to contact the vendor and get an exchange (although, I know that you said that is not possible). Not sure what else can be done though....