Driver Recommendations

I'm very interesting in designing my own headlamp for trail running, however my knowledge around drivers is still very limited.

I want to use 18650 cells, either single or multiple in parallel - so we're looking at ~3.6V. The LEDs that seem to stand out are the XM-L2, XP-L2 and the XHP50.2 - unless others have better suggestions for flood beam style lighting?

My understanding is that Linear drivers are cheap and simple and would pair well with the 3V XP-L2 and XM-L2 3V options. This wouldn't work for the XHP50.2 though.

It is also my understanding that Boost drivers would be a more efficient option for all 3 models? However I can't seem to find any rated for ~3.6V input.

Does anyone have experience in this area and can they recommend me toward some driver options to suit my needs?

Mountain Electronics sells single cell boost drivers. Check those out

Boost drivers do just that, they boost the voltage. You would not need a boost driver to control a 3V LED from a 18650 cell, a linear (7135 chip) or Direct Drive /FET driver will work fine for such a 3v configuration. A reason to use a boost driver would be if you wanted to use a 6V XHP LED (or 2X 3V LEDs in series) from a single (or parallel) 18650. The cost for boost drivers is typically significantly higher that for using a FET/Direct Driver that is configured to control a 6v or 12v single LED (or series of LEDs) from an appropriately sized series battery pack. Boost driver likely makes more sense if you are building a small handheld flashlight with limited space for multiple batteries, on a headlamp with rear head mounted or remote battery pack you are a bit less constrained on number/size of batteries so less of a need for using a boost driver.

You should probably start your project by setting a max lumen level and flood/throw beam pattern that you want to achieve, use that criteria to select the LED to be used, voltage & amps needed, and then select a suitable driver and battery pack configuration to supply the the LED.

I recently built a custom headlamp using a 6v XHP70 with a DD/FET driver and a 2S (6V) battery pack. On high setting, it draws 2.6A and is putting out somewhere well over 2000 lumen from the LED. Optics and sufficient cooling are a bit of a challenge when constructing a headlamp, I really only intend to ever use at sustained max brightness on cold winter nights when low ambient temp greatly helps with cooling the LED.