There isn’t a single document anywhere that i’ve seen that answers all your questions, but in my virtual travels i have found some answers that you seek
There are many reviews on this forum that are great resources and cover many models out there, classified under which battery it uses, they are all stickyied in their respective forums.
I generally avoid ebay lights, anyone can sell anything, at least with a known website they have more of a reputation, in lights sold, and to maintain, not a perfect system, but better then ebay.
Charging to 4.15 volt is actually good, lithium batteries die of old age faster if stored at full charge, and have relatively low self discharge if not used for a few months (unless they are crappy quality), wikipedia can tell you more.
You can estimate lumens based upon the current draw of a light (minus about 10% for led driver), a single xml cannot give over 1000 lumens, after you hit that, any more power you dump into it turns into heat, no matter what any listing for a light says.
Very few people like the strobe and SOS modes.