Yea, the strips are WS2812B ones. I'm planning on getting a 5v/10A power supply to drive them. Adding a MSGEQ7 and use it as a spectrum analyzer is also on the to-do list in my head. But hm, multiplexing would be a cool feature to the project. And, power saving too!
All multiplexing does is send current to one group of leds at a time, then the next group and so on, at high speed. This has the side effect of dimming the leds, and saving power, because each receives less current on average.
The effect is exactly the same as using a lower pwm duty cycle. For example if you use a 1/8 multiplex ratio and each led receives 16mA when it is switched on, it only gets 2mA on average, and its the average current that determines the brightness. This is equivalent to pwm with a 12.5% duty cycle or analogWrite(pin, 32);.
So, yes, ws2812B can use a lot of current, but they don't have to. If you only use low brighness/pwm settings, it will use exactly the same power and give exactly the same brightness as a multiplexed display. But it will be far simpler to build!