RSI(Open,14) - Plots RSI with respect to open values of candles for last 14 periods
RSI(Close,14) - Plots RSI with respect to Close values of candles for last 14 periods
I dont think repainting will happen in case of RSI(Open,close), as any candle has only one value(price) for Open and close. But if its RSI ( High,Low) then repaints are possible as the value of high/low changes during the candle formation.