It sounded like you got annoyed that I was guessing and it sounded like you tried to make it clear to me that the guess was not helpful to you with the use of sarcasm. I guess I misunderstood, sorry.

Regarding the actual questions: You asked how does it compare to Coreboot. Canoeboot is actually coreboot, just slightly modified to work with Free Software Foundation’s rules but these rules are kind of absurd. See [1]. Libreboot is also modified Coreboot but one that’s actually good. The difference between them is that Libreboot should be a bit easier to install and that they support different hardware.

In terms of battery life the same laptop with or without Coreboot should perform the same. Coreboot really only handles the booting. Battery life should depend on the “EC firmware”, which is like a second chip on your motherboard that handles stuff like blinking LEDs or checking if your lid is opened or closed. It also depends on the OS itself so Linux vs Windows will make a difference. Canoeboot is an exception because it does not include “microcode updates” for ideological reasons. Microcode is code that runs on a “CPU inside of your CPU”. Not updating it will A) make your CPU buggy and vulnerable to attacks like Spectre [2] and B) maybe even have worse battery life because Microcode can control the voltage your CPU runs at. More voltage -> more power (P ~ V^2)

[1] https://libreboot.org/news/policy.html

[2] https://en.wikipedia.org/wiki/Spectre_(security_vulnerability)