Dual Booting between 2 SSD?

Few games that work in 7 won't work in 8.1. If you want to dual boot though install 7 first and then 8.1 to avoid boot manager issues.

That's a beautiful system you're planning to build. Good luck with it.

I'm not a gamer so I won't comment on that aspect of your query.

But in terms of creating a dual-boot system you shouldn't run into any problems as long as you take simple precautionary measures. The approach I would use is somewhat different from the one suggested by Dee Kay, to wit...

1. Install the OS (doesn't really matter which one) on the SSD of your choice but ensure that no other drives are installed at the time of the OS installation.

2. Work with that OS for a reasonable period of time to determine all is well - the system boots without incident and functions without any problems.

3. Then disconnect that SSD from the system and connect ONLY the other SSD which you will use for installing the other OS.

4. See 2. above.

5. Then you can connect all three drives to the system, ensuring that they are connected to the motherboard's SATA 6 Gb/sec connectors. While not crucial, it's probably best if you connect the drive containing the OS you think you'll probably be using more often to the motherboard's first SATA 6 connector (SATA6G_1) and the drive containing the other OS to the SATA6G_2 connector. The 2 TB HDD can be connected to the third SATA connector. By & by you can always switch the two SSD connections if you think it desirable.

6. Ordinarily the system will boot to the drive connected to the motherboard's first SATA connector but of course you can instruct the system to boot to another drive by pressing the F8 key (I'm pretty sure that's the right key for accessing the boot menu designated by your ASUS UEFI-BIOS) at the beginning of the bootup process.

7. I note Dee Kay's suggestion that you install the OS you think you will use most on the "faster" Neutron SSD. My own inclination is the opposite - I would use the Samsung SSD. While I haven't worked with the Neutron I have worked with the Samsung 850 EVO and it's a fine SSD. I have serious doubts as to whether the Neutron is "faster". But the truth of the matter is that in all probability it really doesn't matter - both drives should probably perform just about the same in a "real-life" PC environment.