my firmware is now RT-AC66U_3.0.0.4_374.35_4,some people said 3.0.0.4.270.26 is the best one if u don't need USB or openVPN and so on and the wireless speed and stability is the best... If i go back to 3.0.0.4.270.26 and press the Reset for 5 seconds to start a new setting,is it enough to clear all the settings? or need I clean NVram myself using command?