Just want to add something about the affects of custom themes on performance.
I read this thread again and someone mentioned they tried all themes and even "disabled almost all their options". If you use a custom theme and go into LB/BB settings to disable some options this does not, in many cases, affect what a custom theme does. Those settings usually only work on the Default theme. A custom theme's coding can override what settings you have changed in the LB/BB settings page. Manually editing the code of the theme is typically needed.