From my experience with lights zoom is nice but not a must have. I set mine to fill up the field of view in the scope and only zoomed it for long range ID.
Dimmable is very useful, particularly in light fog or heavy cover where a bright light might wash out. I used the dimmer quite a lot.
I don't know how your 24mm objective will work for you, I always used at least a 40mm at night.
