If you're gonna dedicate the hardware to OPNSense or any other router software, then get something not too expensive. A Raspberry Pi 4 can route and traffic shape a gigabit without breaking a sweat, so you don't need much mini PC just to do routing. N150, N100, N95, or whatever are fine.
If you want to combine functions, running something like Proxmox and putting OPNSense on a VM, then get yourself something more capable, Ryzen 5 or 7 7000 series maybe, 16 GB of RAM
@Imaginary_Stand4909
Whatever you get make sure it has 2 NICs, and I like to bond them and put them into a LAG on the switch.
Get a managed switch, low end Zyxel is better and more secure than the low end TP-link, the higher end TP-Links are more featureful than the higher end Zyxels.