I don't have a particular guide at the tip of my fingers, but I can share some recommendations based on my experience:

• prefer a phone with USB-c if you plan on connecting USB things to it. the otg adapters for micro-b are kinda hit and miss when it comes to keeping the phone connected to power as well.
• look out for clearances of those carrier locked prepaid phones from physical stores, you can get nice devices for nearly nothing
• whatever you're running on the phone, make sure it starts at startup, so you don't need to go launching everything if you reboot for some reason
• if the phone is"mission critical" e.g. random restart while in the middle of a print is unacceptable, turn off all the automatic updates and such.
• a VNC server has been helpful, to remotely poke at the phone if I'm too lazy to go do it physically
• get something that'll keep the screen off the phone on. I've encountered reduced performance regardless of what battery optimizations I've turned off without doing that but YMMV depending on ROM.

I fully expect the screen thing and the batteries bring in there constantly charging to kill the phones I'm using eventually, but it's something I expect and accept. my octoprint phones have been fine so far, for a bit over a year 🤷‍♂️