LED strip brightness decreases when using multiple strips
40 amps is a LOT of current. 

24 AWG wire can't handle anywhere near 20A of current, nevermind 40A. (After a little googling, it looks like 24 AWG wire is limited to about 3.5A.) 

Think about it. In the US, 15 amp branch circuits require 14 AWG wire. 20 amp circuits require 12 AWG wire. It looks like 40 amps requires 8 AWG, from the googling I did. (Voltage doesn't really matter when considering current carrying capacity.) So if you want to drive 40 amps, you need 8-gauge wire on both the +5 leg and the ground leg to your LED strip.

As I said in my comment, I found some 144 WS2812B LED strips on Amazon that draw 20A just for one strip. You say your strips have 150 WS2812B LEDs on them. Assuming it's 150 vs 144 of the same LEDS, you're going to need almost 21 amps per strip, so 2 strips will slightly exceed the 40A capacity of your power supply, and VASTLY exceed the current handling ability of your wiring. As a general rule you should have a power supply that offers a little MORE current that your max needs, never less.(When a power supply reaches its current limits its voltage may start to droop, or it may be slower to adjust to rapid changes in load.)

In addition, You're gonna need BIG, THICK 5V and ground wires to feed your LED strips, and you should wire the LED stips in parallel. (I suggest 8 AWG wires for 40A. Those are HUGE, but that's what you need for that much current.) You should not connect either the +5V supply or the ground wires through a breadboard.