A DHCP server gives out addresses to devices that don't have a static address.
A DHCP server has a range of addresses that it is permitted to hand out to devices. You can make the range however small you want, but I believe that the range can be limited to how large it can be.
Static IP addresses do not need to be within the DHCP range.
You could have a range of 192.168.1.105 to 192.168.1.160. Then use The static IP address of a home server as 192.168.1.100.
There are two ways to set a static IP address.
- Manually on the device itself
- Via the DHCP server.
If you want the same IP, I would set it manually on your computer, and make sure you always switch wifi off when you use ethernet. I don't think you can have it switch automatically.