RVR and RV are different.
RVR has multiple sensors looking along the runway, and reported on METAR (or by ATC) depending on the runway divided into three areas (touchdown, midpoint, rollout).
RV is an approved observer. You might not be able to discern as many runway lights as the person standing next to you, so it’s a bit more subjective. And visibility not presented in RVR format in a METAR/ATIS etc is just visibility, and the automatic sensor is not necessarily looking down the runway.
well, that’s my non technical understanding of it anyway. I don’t do LV ops so don’t really concern myself with the RVR technical details!