What solar/wind displaces varies a lot by location. Coal is used much more than gas. According to https://ourworldindata.org/grapher/electricity-production-by-s

What solar/wind displaces varies a lot by location. Coal is used much more than gas. According to https://ourworldindata.org/grapher/electricity-production-by-source?country=~OWID_WRL https://ourworldindata.org/grapher/electricity-production-by... the top 3 are coal, gas, hydro. For places with hydro it's effectively energy storage for wind/solar.