Chosen Solution

I was wondering if I could upgrade my existing MacBook Pro Late 2012 with Samsung 970 PCIe/NVMe SSD.

To my knowledge, No It does support standard 2.5” SSD’s though.

There’s no way to connect it to a Gen 3 x4 PCIe lanes within the PCH. I don’t even think your CPU/PCH has support for that, back then it would have been AHCI/PCIe Gen 2 which is much slower then what your M.2 needs, even if you could connect it… The most speed you can get will be from Samsung Pro SSDs, optimized with Samsung magician in RAID 0, still very fast. I would also do a RAM upgrade to 16 GB if you haven’t done that already. Even if you decide to use only one SSD and upgrade the RAM this will give you the best performance gain for the money.

I think you picked the wrong macbook when asking the queston, If you have the late 2012 retina macbook pro then a good idea would to go here https://eshop.macsales.com/item/OWC/S3DA