How are you current-limiting your LEDs? At that power level, a resistor inefficient. I recommend you use an off-the-shelf LED driver, Meanwell makes a variety of them for example. Also take a look at "Buckpucks", they are inexpensive and popular. Just make sure you get ones with an 'enable' pin, usually the ones that are dimmable have one. You'll need one driver module per string /segment.
Then just drive the 'enable' pin of your LED drivers with the CD4543 directly, no transistors required.