I would look out for a 4 layer Wii: https://bitbuilt.net/forums/index.php?threads/revision-identification-guide.863/ .Also when you are trimming I would recommend to tape over the chips, so no dust gets under the CPU, GPU and RAM.
I just took a little look at the differences in the i2c registers, there are some changes, but nothing that's too big. Reg01 and Reg3 were changed much, the other changes are minor.(e.g. Reg0C the NTC_FAULT got more sates) I would recommend to definitely use the BQ25898D over the BQ25898...
This is one of the best 2s cmbs: https://www.ebay.com/itm/Intelligent...2S-Packs-18650-lithium-Satellite/311721987212
It has all protections and it has a charger build into it, this means you can charge it with 9-15V
The front will fit into 220mmx220 printers, but if you print the back diagonally it will be to close to the edge. You would need to print like Tropper348