Hi @planetbob99 - With the TerraMaster F8 SSD Plus there is an internal USB port with a 4GB USB key (its on the CPU side of the motherboard), this houses the install files for the TerraMaster TOS, and you are correct, this is designed to be installed on part of the first NVME that you install.
However, as TerraMaster allows for third party OS's to be installed, you can remove TOS USB key and install your own and use it as the primary disk for the OS install, that way all the nvme's can be used for storage. As Truenas recommends an actual drive rather than a USB key, I decided to use a small 2230 nvme within a USB case with a short USB cable with a right angle port, it fits quite well and I have it stuck the the chassis with double sided tape. The only downfall to this approach is the internal USB runs at USB 2.0 speeds.
Another approach is you want redundancy and don't mind using the nvme drives would be to reserve nvme port 1 & 2 in a mirror raid and use that for your OS, then you still have 6 nvme's to play with.
For me, I just wanted to max out the system ๐ I'll post a pic when I power off the NAS.
It has been running fine for the last couple of weeks, with Plex running in the background with a couple of movies and TV shows. Still plan to wait for V1 before migration.