As far as lag goes, have you looked in the running services tab to see what's slowing it down? (Settings>application manager>(swipe to) running services?
If you have too many apps running constantly in the background you will run out of ram and it will lag.
As far as battery savers go, in my experience,they do more harm than good... and most (If not all) will slow down your processor (this is one of the ways they save battery)
You could do most/all of what the battery saver does manually (and probably more efficiently)
Things you can do include
-dim the screen when not in direct sunlight/bright rooms
-turn of sync
-turn of mobile data when its not needed (not for everyone since it wont connect to the internet etc)
-if you use a live wallpaper, switch to a regular one
-freeze apps that run in the background when you're not using them. (Facebook, maps and anything else that runs in the background will drain the battery by pinging for updates or in some cases causing wakelock)