I would have to agree with bsms. In western (outside of arena events and just for fun/trail) the horse's head should be able to move freely to balance itself. I guess I've always looked at it that the western form of collection is a balanced horse that's not going to trip, fall, or stumble and knows how to move its body to achieve this, I could personally give a darn where it's heads at to do so.
I ride with one or two hands (it depends on the horse and day), but I always make sure I have a fairly loose rein (depending on the horse, some like a tighter rein) but always control. I personally prefer to neck rein and achieve it that way but I know many people who use two hands. You legs will be farther off the horse so that might take some adjusting, and I've found (at least in my western horses that I've ridden), your seat is a major component.
For instance, with my mare (who's just a trail/cow/pleasure horse) if I got to canter all I have to do is drop my reins slightly till my hand barely brushes her wither, and then shift my seat up like she's already started to canter. Without fail she goes into a nice lope, to extend that and go faster I simply sit back a little more and give her more rein and to slow her I sit deeper and say "easy". I ride both disciplines and I've found very few differences in them other than how they look. Whenever I go to a dressage barn I've gotten compliments on how quiet my hands, legs, and cues are. (I'm attributing that to the years spent with no contact on the bit, a stubborn horse and any leg at all sends you flying into the nearest bush lol).
I would also like to just add: quiet hands. I see quite a few english riders take lessons at our barn and the minuet they get into a western saddle their hands flail (neck reining and/or holding with two hands are both equal culprits lol). I think it's from all the western movies they watched prior to the lesson....
And maybe It's personal preference, but I find when I do the toes to the center (like in dressage) it interferes with my leg and communications to the horse. I like my toes out (keeping my leg off of my horses). Other than that my leg is more or less centered underneath me.... but it may be a bit more forward and out more.
Have fun and enjoy!