Check this CORDEX East-Asia site for RCM data. They have multiple RCM-GCM_RCP combinations. https://cordex-ea.climate.go.kr/main/mainPage.do .
It would be helpful if you add further details on the kind of impact you want to assess. But you can use your observed Precipitation and Temperature data to assess the credibility of the RCMs during historical periods and look at future projections from those you feel comfortable with. You can do whole lot of different analysis like trend, mean change (future vs historical), impact on extremes indices (like the ETCCDI), ....