PRIME Z790-P multiple NVMe drives

[Kalidrenlol]

Hello community!

I just finished building my new PC, and since it has been a while since I did this last time, I'm a bit confused about the M.2 slots and storage using them. I have a PRIME Z790-P motherboard with multiple M.2 PCIe 4.0 X4 slots available. Currently, I have a 2TB NVMe drive in the M.2_1 slot (the one for the CPU chipset, I think?). I was wondering if I could add more drives to the remaining M.2 slots. I read something about a performance hit if you do that, and the drives might end up only using x8 or even x2/x1 PCIe lanes. I also read something about it possibly making the GPU run at 8x PCIe lanes.

Again, I really don't know much about this, and I couldn't find a conclusive answer on the web. So, to sum it up, can I add additional NVMe drives (preferably 4TB ones) to the remaining slots on this motherboard without the risk of compromising performance?

PC Spec:

• Motherboard: ASUS PRIME Z790-P
• CPU: Intel Core i9 13900K
  
• GPU: Palit GeForce RTX 4090 GameRock
• M2 Drive: Kingston NV2 - 2TB SSD NVMe - PCIe 4.0

The layout:
 

[JohnAb]

Yes, you can use the other drive slots as well. Your motherboard manual might say if the GPU slot will drop to x8, but even if it does, somebody told me recently that the performance hit was very small - less than 3%. On my 690 Hero, I have all slots filled and I'm still on x16. It depends on the motherboard.  So if you want the storage and the speed falls on the main GPU slot, you probably won't even notice. 

[Silent_Scone]

As per the manual, only M.2_1 uses CPU lanes. The other onboard slots use the DMI, so will not impact GPU operation.