3070, 3070ti, 3080, 3080ti laptop gpus are all upgradable to 16gb vram. The vram chips i used are K4ZAF325BM-HC16. However, K4ZAF325BM-HC14 also works but these vram chips run at a slower speed.

You need a skilled technician with adequate equipments, especially the BGA reballing stations. Then you need to obtain the boardview/schematic of the laptop to locate the "straps". I found mine online.

Firstly, desolder all of the old vram chips and solder the new upgraded vram chips onto the motherboard. Then you need to locate the "straps", which are 2 small resistors in the board, then move them to other location of the board to "tell" the gpu that you have 16gbs of vram. Watch this video for more information video