but I personally find existing religions I have looked at (mostly Christian religions) insatisfactory and haven't found the need to dig too deeply into what else is out there.
You should take into account that those religions appeared hundred, yet thousands of year before you. They are custom made for the population of that time and they should have basic ideas that their brains can understand. So those religions may not meet your expectation. But, this in itself, is not a reason to say "God doesn't exist". You should dig somewhere else.
As I find with many atheists, I believe there may be some higher power
Scientifically speaking, there are not sort of "higher power".