You might be right, Arne. I've never done any comprehensive comparisons and apparently nobody else online (outside of ASUS) has either, lol. I just have the gut feeling that increased electrical distance (balanced across a compromised "longer" path) can only increase dB signal loss that tiny little bit more = slightly increased overall latency at the high end. Perhaps no difference, perhaps a difference that is indeed real but immeasurably trivial.

OP has done good research. Although I betcha he'll have a mild heart attack when he sees the size of the box on that 1000D, haha.
https://www.youtube.com/watch?v=DqkFNpngDSE
https://www.youtube.com/watch?v=WRPmykpEJfA

My advice was just based on a little budget stretching ... I think smallish-and-fastest system M.2 plus largish-and-kinda-fast games SATA would be roughly equivalent performance and more storage capacity vs a middly-sized-and-fastest M.2 for everything, same snappy OS and still no loadscreens but more space for games. Ideally you'd want to populate with biggest-and-bestest-and-fastest drives everywhere but then your costs escalate alarmingly.

There's also other merits in multiple drives - M.2 is serviced by hardwired PCIe3-to-CPU while SATA is serviced by PCH-to-to-CPU - so that more data can be accessed in parallel without deep command queues on a single drive, without bandwidth becoming saturated on one bus, and with the bandwidth spreading the love across CPU threads instead of bottlenecking as often. Plus, migrating your entire games/apps library to another machine is as simple as swapping a drive. (But there's also a tradeoff - PCH-to-CPU can be saturated if you fill it up with tons of bandwidth-eating USB junk or motherboard-serviced hardware.)

You can certainly choose other SSD configs without going far wrong. You already know the size (roughly) of your games/apps, don't forget that Win10 keeps growing and growing in size as it updates itself, and you'll start to notice peak drive performances drop when the system drive is more than half filled. 32GB RAM is enough that you won't have to worry about the OS eating up big swaps (unless you segment the RAM down with RAMdrives and RAMcaches and stuff, or you run hoggy VMs).

There are apparently some UEFI/BIOS settings you need to check over *before* you install your WinOS ... so that your WinOS software and your platform hardware aren't permanently married to each other (a marriage which causes issues whenever it's time to change Windows or move Windows to another platform or change motherboard). Sorry I don't know specific details about this - I don't use WinOS garbage outside of virtual machines - but it's a heads up lol.

One more question: Am I gaining anything with this Mobo and my current setup/planned usage as opposed to a lower priced Maximus VI Hero? Will I gain that much more from the Cache speed on the Extreme?

I’ll just drop my .02 here on drive choice. You want the fastest load time that’s within the low que 4K random arena. I’m not talking about the likes of Samsung with astronomical sequential reads that does well with synthetic bench marks and little else. Fastest drive available within your drive budget would be the intel 905P U2 drive that can be run from U2 or be ordered with an NVME adaptor. Worst performance comparisons they still quadruple the Samsung random 4K speeds. 480GB is running about $500USD ATM. The PCIE of the 905P has double the capacity and more than double the price though.**