Lipos can be use both brush and brushless motors.
lipo packs in parallel connection is ok to use on wall-e or any battery operated toys or devices.
wall-e doesn't like rough pavements. dont ever let your kids play him there. he likes smooth tiled floors, carpets. or any smoother surface areas. one of my kids wall-e got one of its gears broken when he was used on rough pavement. after that incident wall-e can't perform to dance perfectly anymore luckyly i was able to repair it. i made the broken part much stronger. he's now dancing perfectly.
there isn't enough room for extra bettery pack inside wall-e body.

well that's all i know about that toy. take care of your ultimate wall-e. sry to say there arent any experts to help us around here. we're on our own. there arent any aftermarket parts for wall-e so this toy is simply expendible so goodluck.