Just let me post more about.
I am now posting this message with latt -c180 running(RIFS V3 now).
RIFS v3 run with very very little lag(I don't feel).
RIFS v2 has little lag.
RIFS v3-RC1 lag mouse stall.
RIFS v3-RC2 completely hang.
(Haven't posted yet)RIFS v4-RC1 completely hang, kernel halt(So RIFS v4-RC1 will be thrown)
BFS lag mouse stall.
For low configuration box, better to use RIFS v2
For normal configuration box, better use RIFS v3.