What SSD storage-drive addition fits into this model of laptop? (HP Omen 16)

I have no idea.

I'm coming here looking for answers, is there any way of determining the upgrade potential from the laptop specifications above?

Tech said I could bring it in for examination to make sure before purchasing, so all else fails I'll do that.

But surely there's a way of knowing from the laptop model code, etc?

I put

m.2 nvme ssd

into amazon and get a list of chips.

Any one of these will do?

I got a tech to open up the machine;

Second slot is present.

Would a Gen 4 PCIe be compatable with this machine?

HP - OMEN 16-c0500na 16.1" Gaming Laptop - AMD Ryzen 7, RX 6600M, 512 GB SSD

A post above says one slot is Gen 4, one is Gen 3...? (was this information in the manual?)

Wait.... this is making less and less sense.

If the processor is what it is, how is one slot going to support gen 3 whilst the other gen 4?

The CPU has it's own read/write speed, but that's different for different slots on the same motherboard?

And does my rig, Omen 16 c0000 have one gen 3 and one gen 4?

I've been round and around with this question with HP tech support, they think not, that it's all gen 3, but the youtube link above claims yes?

Because answers are so conflicting/ambivalent (numerous lanes and mapping....? I'm not a computer tech).

But it doesn't matter at this point, ordered the WD blue SSD.