You’ve got more than three. There’s the A-hole, P-hole, V-hole, M-hole, two N-holes, and two E-holes. Then there are the manufactured holes: two H-holes when you make a fist, a TT-hole if you squeeze them together, a BB-hole if you’re on the heavy side, and two T-holes for those with foot fetishes. There are up to 3 bonus holes if you have one or more of the various medical stoma, and two extra bonus holes if you’re blind and have prosthetic eyes.
But you can get by with only one if you tie those sausages together end-to-end.
Start by defining your available power. How many watt-hours can you generate? A small 100W solar panel can provide an average of 400Wh of energy per day in the winter. That’s more than enough to run a 10-inch tablet 24/7 and LED lighting at night. I’ve seen 360W solar panels for under $100 on the used market. That’s a couple of KWh a day. Even a 100W bicycle generator and a 30 minute workout would power a tablet for 8 hours.
If power consumption is that big of a factor, perhaps separate devices for video, music, and reading would be beneficial. A dedicated music player can consume less than a watt. An e-paper reader requires fractions of a watt.
I have a folding 100W panel, a 30Ah 12V LiFePO4 battery, and a charge controller that I use while car camping. It keeps all the electronics running for a group of 4 without relying on a noisy generator. The battery is big enough to compensate for a couple of rainy days.
My backpacking setup is a 15W panel and a 30Wh battery. That kept my phone and flashlight charged for 2 weeks on the Pacific Crest Trail.