"Tiny" build -- meaning you've probably got a relatively ancient or underpowered router -- which either or both won't have enough flash and RAM to install and run wireguard, or enough CPU power for more than a trickle.
I'd suggest reading up on a new device and then, if you've got questions about specific units, searching on the forums here for opinions. If they aren't already answered, opening a new thread with your question would be a next step.
Many opinions on devices in the US $20-50 range (or less) that are likely going to be a better option for you in the long thread