Yes, you can use both Ethernet ports on a second Eero Pro router to connect different devices. However, depending on your networking setup, the role of the ports may be different.
If you have a modem connected to your first Eero Pro, the ports on the second Eero Pro can be used to connect additional local devices, such as your laptop, game consoles, or media streaming devices.
On the other hand, if you don’t have a modem connected to the first Eero Pro, then the ports on the second Pro can be used in bridge mode to connect two networks together. This is especially useful if you are using Eero Pro to connect two different networks.
In either case, it is important to remember that devices connected to your Eero Pro router will only receive the benefits offered by Eero Pro if they are connected via WiFi. So, if you want to enjoy faster speeds and better coverage, devices connected to Ethernet should also be connected to your Eero Pro via WiFi.