When it's on, the backlighting can make the edge of the screen obvious if the monitor isn't filling the mirror, but if you use a PIR or other motion sensor, when the screen is off, it's pretty seamless. Using a quality vinyl over the non-screen sections is critical. This one is often recommended and it's what I used- Vinyl Frog vehicle wrap.
This is the kind of stuff I'm talking about: VINYL FROG Vehicle Wrap Vinyl Matte Black Stretchsble Air Release PVC DIY Decals 12"x60" https://www.amazon.ca/dp/B073XM98RK/ref=cm_sw_r_cp_api_i_Mw-iCb98XMFSH