Good start.
In general, you don't want a gaming board. Some things are less than suitable for a NAS, like audio or more than a few USB ports. (TrueNAS & ZFS don't work well with USB attached disks for data pools, though boot pool can work on USB.) Plus, on occasion gaming boards default to over-clocking CPU, Memory or PCIe ports, which can be problematic for a server on 24x365. But, if you have it already, or like Gigabyte boards, it may work fine for you.
You use the term "Raidz0", which does not exist in ZFS. Perhaps you meant Striped vDev. But, you could have just as easily meant Mirror vDev. Thus, I suggested reading the "Terminology and Abbreviations Primer".
Which TrueNAS line were you thinking of using, Core, (based on FreeBSD), or SCALE, (based on Linux), which also supports Apps.
Now if you can describe your use cases for each pool.
Then what are you going to use for your boot disk / pool?
Boot devices in general don't need to be very large. For example 16GByte to 32GByte are perfectly fine. But, if you use a SATA SSD in a ZFS Mirror, and use TrueNAS SCALE, then having 64GByte or 128GByte can be useful to have all the Linux swap on the boot devices.