Replacing the M.2 NVME's for more speed and storage

Hi,

opened up my Samsung Book 2 Pro 360, to check out the storage (I have the 15.6 inch version, 16gb ram and 512 NVME)

The motherboard has two M.2 Slots, only one is occupied with a 2280 formfactor:

M.2 NVME type SN530 SDBPNPZ-512G-1004 (which is a PCI Express 3 x4)

The 2nd slot seems to be a 2230 formfactor (right?)

I am looking to replace the existing M.2 for a larger, PCI Express 4 x4, 2TB Samsung 990 Pro or 4TB Western Digital black if they go down in price a bit first, which should give a significant boost in speed and storage capacity

My questions:

1) Are both slots actually PCI Express 4, or is the 2280 formfactor PCI Express 4, and the 2230 formfactor PCI Express 3?

2) Is the smaller M.2 slot indeed a 2230 formfactor?

3) As there is no room for heatsinks, are the target NVMEs suitable, and what advice would you give for the thinest possible, but best cooling for the NVME's?

Thanks for any input!