I've almost the entire profile canvas layout redone with Bootstrap 4 classes. This eliminates roughly 50% of the custom CSS applied by CB. Check out the progress below.
The biggest takeaway here is the massive improvements to the tab menu and the cb menu bar. Currently there's scrollers that scroll left/right if there's too many menu items. The reason this was done is due to positioning behavior of the menu bars. They had no overflow handling because they couldn't due to absolute positioning offsets. These issues are eliminated entirely and both CB Menu and Tab Menu can overflow perfectly fine allowing for A LOT more menu items to be visible and easily used. The responsiveness of the canvas layout has also been significantly improved (am still making responsive improvements too!) so it can work better on smaller screens.