:facepalm:The 74HC138 and the '154 are decoders/demultiplexer that are addressable with only one pins at a time. I am not clear if you are lighting LEDs or characters. You could multiplex for each character and PWM the brightness if each character with a pass transistor if you have a common anode display (or wire individual LEDs as a common anode). All options are possible.
Yep. duh. of course they are. brain fart.
And individual LEDs, not characters.
OK, so I think I have a plan here.
Now I just need to decide on a MCU and bluetooth chipset