Everyone's advice is great. I'll just add:
- DON'T get information overload. Ultimately, the best "concept" is the one that you can stick to.
- Work with what's going on in your life right now. I've been successful while having the luxury of only working part time, I've done it while unemployed and terribly broke, I've done it working full-time on my feet, and now I'm doing it while working the almost-midnight shift. It's a grind, but I've learned to do what works. We go through lots of lifestyle changes in life, some long-term, some short-term - your kids (if you have them,) relationships, homes, jobs, seasons. Go with what your lifestyle, budget etc is right now and don't be afraid to have different tools in your toolbox for different circumstances.

On the topic of assuming food reactions based on scale weight gain during the day... I'm not sure it's accurate. Aren't there too many other confounding factors? Exercise, how much water you drank, occasional medications like ibuprofen, humidity (ie how much water evaporates from your skin), saltier foods vs very little added salt, high-fiber foods, etc. If it were me, I wouldn't draw conclusions unless I was weighing, measuring and recording everything that went in my mouth, including water. The reason most of us stick with first-thing-in-the-morning weights is that our bed time routine tends to be repetitive and steady, unlike our waking hours.