In my personal opinion, I dont think a lot of tweaks will drain your battery unless there was some type of corruption during installing. Themes can drain battery but only themes that are very very poorly designed: huge file, memory leaks,ect.
Just make sure you install everything one at at time and make nothing is still loading in the background when you hit "confirm" tap install, let everything load, make sure that little spinning wheel in your status is gone before tapping confirm. I have had and over 20 tweaks and mods installed with no extra battery drain. If you notice battery drain after installing something, then reinstall, but remove first then install instead of just hitting reinstall. What sux is that some these mods get corrupted during installing and one piece of code doesn't change the file it was suppose to, and even when you uninsall that mangled code resides which leave your battery draing even after you uninstall something. Be patient.