I know most guys will use a rack and set pins to do parials. I prefer a reg BB, or even DBs (which I find myself using with more and more frequency laely). If you can set pins in a rack (or even a smith, as a buddy of mine uses, and goes well over 500 on it, and he's in his 60'!) you will be able to handle a lot more weight.
I don't worry so much about the poundages at the moment, prefering to hit my lower back at the end of my session, after it's already been worked a bit with BB rows and T-Bar work.
If using a BB, I will not go above 3 plates (which is light considering what I used to pull).I start with the bar on the squat rack (waist height), unrack it, and will slowly lower to just below my knees.
SOME PEOPLE WILL FIND A LOT OF STRESS ON THEIR BACKS. If so, don't go down so far. If my own back is hurting, I will definiely shorten the motion.
If using DBs, I actually like to retract my scapular a bit at the top portion of the movement, and get an extra little squeeze in my upper mid portion.
Each person will have to see how far they can go ROM-wise. Again, some folks will experience more discomfort from doing partials, most likely because they're trying to move weight they previously did, except that now they've eliminated a lot of the 'helper' muscles from the equation.