Note, on the power resistors, I recommend searching for these values (one value at a time):
… You might only need a few of those values.
SPI displays with touch-screen
… modify search to your needs; those without touch-screen cost around $5 and up.
Oh, and about the boost converters:
If your input voltage is higher than the desired output voltage, the output voltage will be the same as the input voltage, so make sure you always keep your input voltage below 12V!
2V .. 24V -> 5V .. 28V boost converters
3V..32V -> 5V .. 35V boost converter
Assuming you’re using 3 batteries connected in series as input to the boost converter:
If your input voltage is normally above the output voltage you set on the boost converter, you can increase efficiency by adding a single Schottky diode from input to output (eg. Anode at input, Cathode at output).
This will bypass the boost converter, when the battery voltage is above the set output voltage, so the power consumed by the boost converter, will be reduced.
-But when the battery power drops below the output voltage on the boost converter, then the boost converter will kick in and start working; draining the battery-string until it reaches around 2V.