A-Furry-Peanut

Yes. You effectively have 32 PCIe 3.0 lanes from the CPU.

There are separate lanes coming from the CPU directly, and from the chipset. The CPU has 16 PCIe 3.0 lanes, the chipset has 8 PCIe 2.0 lanes.
 
The full-size PCIe slots on the board will take the lanes from the CPU, while the other slots will get lanes from the chipset.
 
Since you want PCIe 3.0 for your M.2 drives, you'd have to get CPU lanes for them. It's clunky but possible. And I'm not sure you'd be able to boot from the drives.
 
Edit: Also, your board happens to have a PCIe bridge chip that doubles the PCIe lanes from the CPU.

We can only speak as to our own products, but when it comes to the IronWolf Pro, all capacities are the same speed, 7200 RPM. The cache does vary a little by capacity however, with the 2 and 4 TB models having 128MB cache and all larger capacities having 256MB cache. The Pro also comes with RV (Rotational Vibration) sensors built onto the drives regardless of which capacity you go for.

It's the standard, non-Pro IronWolf where you're going to see speed change with capacity: 1-4 TB models are 5900 RPM and then larger capacities are 7200 RPM.

No matter which route you decide is right for your needs in the end, thank you for considering Seagate!

As stated in the quote you supplied they have given the information required to know which kind of JBOD it is. It states "JBOD to use the drives individually" so this would not be a span configuration, you will see both 2TB disks separately in disk manager.