ok lots of questions and a lot of info.
Lumens - this is a bit like torque in a car engine. More is always good, but won’t tell the complete picture.
Lumens is amount of light, now some ratings are at the LED (no losses) and some are OTF (out the front). The head, lens and reflector will cause some lumens to be lost. So OTF is always lower than LED lumens.
ANSI FL1 is a standard and takes an OTF reading at 3 mins (iirc). This is done because some lights are very bright initially but will sag due to heat, cells, voltage. It’s done to help create a more comparable lumen figure.
Some budget Chinese lights however claim theoretical lumen output or just plain lie about it, so make sure you know what you are comparing too.
As for how bright a light is, it depends on if you want throw or flood beam profile. An XM-L offers the most lumens, but it’s a big LED and has low surface luminescence. This means in a small light it will offer up lots of lumens, but be very floody and not throw all that far. A lower lumen XP-G emitter in the same light will likely throw further but with a smaller hot spot and duller spill.
With regard to the PA10, well personally I’m not overly keen on JetBeams marketing claims - they seem rather false and missleading.
The PA10 is a 1xAA light that offers up 140 lumens and being an XM-L will be quite floody. To get 650 lumens you’ll need to run it on a li-ion 14500 battery (looks like an AA but is a different chemistry and needs a special charger).
This introduces some problems, the PA10 then loses all it’s modes and direct drives the LED. You get massive output, but it’s pretty useless as you’ll have no other modes to use.
Being a small light you won’t be able to run it on 650 lumens for more than a couple of mins at a time, there will be way too much heat.
Heat is going to be an issue for any small torch, so this is not unique to the PA10. But it’s something to bear in mind that almost no single cell light will be able to sustain 600 lumens out put due to heat.
If you like the PA10 form factor but want a more usable light you might want to consider the PC10, it uses a CR123A or an RCR li-ion. It makes 550 lumens on the li-ion but retains all its modes so is actually usable. It is however still a small light, so will be floody not throwy.
If you genuinely want 600 lumens maybe something like a Klarus XT11 or Solarforce L2 would be a better form factor. Just about pocket sized but more able to cope with the heat.