Yes, however it is important to note that in every network, you must use an eero with an Ethernet port on the back so you can connect it to your modem.
eeros that can be used as a gateway are the eero, eero Pro, eero 6 and eero 6 Pro. Once your gateway eero is installed you may use any combination of eeros to setup your network.
All eeros are compatible with each other no matter when they were released.