Some things that might help might be to jot down answers to these sort of things:
-What sort of power source?
There are lots of options such as AAAA, AAA, AA, CR2, CR123A, RCR/16340, 14500, 18350, 18500 or 18650. They all have differ pros and cons such as size, shape, length, voltage, price, availability and so on
-Run time
This will be linked with the battery you use. If you want more run time then you’ll need bigger batteries and/or lower output
-General size and shape
Again this will be linked or rather determine what batteries will be suitable. Do you want it short, narrow? How bulky?
-Beam profile?
It’s usually a trade off between spill and throw in terms of how and where the light is directed. You can rarely have both flood and throw. That said enough lumens in flood can still have a good beam distance, but that’s not the same thing as a throwy beam profile. A good example is an old in Mini maglite; focus the beam into a tight spot and it’ll throw the beam quite far, but only light up a tiny area on the target and have very little spill. If you take the head off in candle mode it is now a flooder, it’s lighting up a larger area but with less intense light and has only a fraction of the beam distance ie does not throw far. If you could up the brightness by 100 fold while in candle mode it’d still light a large area and it’s had a greater beam distance, but it still wouldn’t be a “thrower” in terms of beam profile.
What you need to decide is what kind of beam you’d like, do you want only a very bright hot spot and no spill (max throw). A Brighton hot spot and moderate spill or a more even distribution between the hot spot and the spill? You can even make a light that has no hot spot at all and is just a large even light distribution.
The thing is, personally while the actual LED itself will have a bearing on flood/throw a lot of it is to do with the optics
Eg
Smooth reflectors (SMO) will throw the best (for normal reflectors), however they’ll have the dullest spill and a bright contrast between the hot spot and spill. Normally the hot spot will be tight and bright with a SMO but they can be prone more artefacts in the beam.
Orange Peel (OP) is a textured reflector, these smooth out the beam and typically offer a larger diffused hot spot of less intensity, but a brighter spill and more gradual transition. They are usually more artefact free but the down side is they won’t throw as far and the OP means a slight lumen loss overall. There are different degrees of OP such as Mild Orange Peel (MOP) and Heavy Orange Peel (HOP). As well as hybrid rectors that might be part smooth and part textured.
The alternative to regular reflectors are the use of optics. You have TIR (Total Internal Reflection). Led Lenser uses these which are movable to offer “zooming”. But you can set them up as a static lens if you prefer. The other kind is a domed lens known as an aspheric lens. It delivers similar results to the TIR but with some subtle differences.
-Emitter.
Ok so this is still an important choice. But a few key points to consider; the larger the LED the less throw you’ll get for a given reflector in terms of beam profile but maybe not outright beam distance. So in a compact pocket light an XML might offer the most lumens, but it won’t be able to shine as far as either the same LED in a bigger torch or a different smaller LED in the same torch.
Lumens. I think it’s easy to get carried away with wanting the highest, but when you consider all of the above you may find that it isn’t always the case. For example an XPG in HOP is likely to offer a smoother floozy beam than an XML in a SMO given a 17mm reflector.
-Brightness. Max output can be great, but what sort of use would be typical? In a house or close up work a bright light will be blinding. Also a highly driven LED will produce more heat quicker and reduce run times.
-Modes. Do you need any? If so what kind? Different brightness settings, blinking modes? Linked to max brightness, if you want lower modes think on how bright or dim. Also some drivers use PWM rather than constant current. This might or might not be an issue depending on use.
-UI. Do you want forward/reverse clicky buttons. Twisty? Side switch? There are also a number of different types of UI such as multi button setups.
Quite a lot to think about I reckon 
