In every one of these threads: "why not a NUC!!?!!"
If you ever hope to deploy a bespoke board with whatever SOC you're using on it, you will never select an Intel or AMD chip. The level of supporting componentry is an order of magnitude more expensive, difficult to obtain, and not publicly documented.
You could spin an RK3399, RK3566, RK3568, RK3588 board today with nothing more than the SOC and potentially the accompanying PMIC (most of these SOCs and blessed PMICs have mainline Linux support): you cannot do this with the x86 chips.
It depends. I am also testing N100 (and N97) machines, but for other reasons. Pricing will vary a lot depending on the number of interfaces, case, etc.
Just pick up an N100 with 4x2.5G ports.