I run Bitcoin Core node headless on one or sometimes two Raspi 4B with 8GiB RAM, depending on what I want to do. Usually I also run Electrs or Fulcrum as personal Electrum servers.

Bitcoin Core as full unpruned node and Electrs now barely fit on a 1TB SSD for the Raspi 4B. Fulcrum fully synced as noticeably faster Electrum server doesn't fit with unpruned Bitcoin Core anymore on a 1TB SSD but needs a 2TB SSD which is then comfortably big enough for quite some time in the future.

For me this is fast enough to use an Electrum or Sparrow wallet connected to my personal Electrum server (I care about address privacy of my wallets).

The Raspi 4B with 8GiB can run with no issues 24/7, consumes ~4-5W on average (or even little less than that) with a suitable USB3-SATA-adaptor for a low power SATA SSD (the Raspi 4B has a total power budget for all USB ports combined of ~6W, power hungry SSDs will eventually give you headaches and unstable operation).

If I had to buy a Raspi now, I'd take a Raspi 5 with 16GiB RAM and attach a 2TB NVMe M.2 SSD with a suitable daughter board. This setup is faster and should work fine 24/7 reliably. You could also run it with GUI if you need to.

Almost any Mini-PC should also work fine and you have more options for RAM size and how much processing umpf you want.