Trying to run a project off of 3.7v instead of 7.4v to save space any advice on picking the right converter w/ regards to current output?

teensy 3.6
PWN for more 4 or more led's depending
neopixels (not sure of the setup yet or how many i will be using exactly)
Blufruit LE SPI
prop shield w/motion
(dont need to power the temp sensor or the altimeter. Since i'm running neopixels instead of apa102's i wont be using the led driver i will be using the 2w amp, maybe the flash memory, and the motion sensors.)

I know the led driver runs 5v...I assume the 2w amp does...if it doesn't does that mean then that the only thing i am running that needs the 5v would be the neopixels? Do i need to run power to 5v on the prop shield if i am not using the led driver and 5v buffers? Or do i still need it for the Amp....

Need advice, suggestions.