Hi Puneech, it is hard to narrow down with doing tests.
But for JuiceDenfender, it is probably not necessary at all. If you want to have longer battery life, just remeber to9 disable wifi and mobile data when you are not going to use them for next a few hours.
Antivirus is not essential for Android. Just try to install apps from trusted sources (e.g., Play store).
You can try to turn on Chrome as it provide better browsing experience than the stock one.