look at used XPS line laptops. they have USBC TB3 that can have a ceiling of 40gbps throughput.

this means you can have a newish gen i7 with 32-64gb of ram with a hub for your networking and storage with a 40gbps bandwidth for it to pipe through. most of that will be available to you since you’re not using it for video out.

keep in mind, Thunderbolt cables/hubs are graded and length of the cable will wreck your bandwidth ceiling. shorter is better. shielded is better.

I once had two XPS laptops networked over TB3 and was getting 10gbe on a 6ft cable. shorten it to a 10inch cable and it would have been likely 40gbe.

they do get warm, make sure you have good airflow and a decent pre-filter and you shouldn’t have any problems.

the standalone laptops will usually run on 100-115w but using a TB15 dock you’re looking at 125-270w. the TB15s are finicky on Linux so you might be better off using a TB3 rated pocket hub with power passthru.

good luck.