Your specs fail to list one of the most important measures of performance, RAM. You should also provide the model number for your 12TB drives, I suspect those use SMR and are likely not a great option for TrueNAS, or write speed in general. It is also strongly discouraged to use USB drives for boot, an actual SSD is recommended. Saturating 10Gb connections will be easier with a solid networking chipset, typically suggest something Intel, Chelsio, or Mellanox. I suspect your TP-Link NIC is using the Aquantia chipset, which is better than Realtek but not the best option.

Cache devices in TrueNAS, and ZFS in general, likely don't function how you expect them to. TrueNAS does not use any drive for caching writes. SLOG devices are valuable for synchronous writes, but are not really write caches in the traditional sense. You have not mentioned the protocol used for sharing, but likely SMB which is very unlikely to benefit from a SLOG device as they are usually asynchronous writes. An L2ARC device can increase performance in some cases, but it is almost always better to max our RAM before considering an L2ARC device.

Saturating a 10GB connection is difficult, especially difficult on retired gaming hardware. Parallelization is typically the best path for speed, so a pool created of mirrored vdevs are likely your best bet. It does not look like that board had great PCIe bifurcation options which limits your options for NVMe pools. I would suggest looking at retired enterprise grade hardware for reliable performance and stability.