here's my update on the issues i'm having after 4.3 update.

apps random crashes - most crashes are SOLVED with manual updates / redownloading the apps, others persistent crashes could be solved with factory reset and redownloading the app

gallery lag and freeze - SOLVED by backing up the sd card, and doing a reformat on the sd card.

significant battery draining when using - 

wifi connections showing unstable -    tested the wifi problem a few times with different wifis at different location. and manage to reset my home modem a few times, and even adjusting the modem channel, to see whether its my modem problem or phone problem. seems like a phone problem to me. the wifi shows that its still connected, and running, and i might still b able to on9 with the connectivity. but notifications show "wifi is unstable" and prompt me to "auto connect to other available wifi". dint experience this problem b4 update.

conclusion: will go for a factory reset to see if it solves the other unsolved problems. but doesnt seems related with factory reset or not