Well this comes as a surprise!! If you go to the Windows 10 Mobile devices supported features page, Lumia 550 is not mentioned as one of the devices supporting Project My Screen over Wi-Fi, but with the Windows 10 Mobile & PC Build 14328, Lumia 550 can project screen over Wi-Fi.
We just reported about Project My Screen over Wi-Fi finally working, if your phone and PC both run Windows 10 Build 14328. And when we checked on many devices, Lumia 550 was able to do it with ease. Officially only these device have support for this feature.
Projecting your screen over WiFi: Lumia 950, 950 Dual SIM, 950 XL, and 950 XL Dual SIM
So that brings us to the question whether Lumia 650 is also able to do so?? If you have Lumia 650 and it runs the latest Build 14328, do check and let us know in comments