I usually recommend beginners to start with a consumer plastic router and a regular PC as server.
A consumer router with 16 MB of flash and 128 MB of RAM running OpenWRT will be able to do pretty much everything you need from a router including port forwarding, DNS, DDNS, adblocking (like pihole), traffic shaping etc. They can usually be found super cheap and with even better specs (flash and RAM).
A regular PC will use off the shelf components that are cheap to buy used and easy to replace. It also lets you use regular 3.5" hdds as well as 2.5" hdds, ssds, nvmes and anything in between, and it doesn't use USB for that, which is unreliable and prone to a million issues.
Again you don't need super specs for the PC either, the smallest NVME you can find for the system drive and 8 GB of RAM plus a gen 6 Intel CPU will get you started and you can probably get this used for $50.
Use the PC for storage (NAS) and for hosting services, the router for network management, DNS and adblocking. If you know any Linux use it. If you don't, install a ready-made tool and use that.
Buying USB enclosures and mini-pcs limits your options and ties you to cramped, unreliable and proprietary hardware.