I want do some brazing. Most likely with a silver filler metal. I have one of those single disposable propane tanks. Is that sufficient? Would a MAPP disposable tank be a better idea? Again, if the fuel supplied from a single tank(no oxygen tank) is it possible to manipulate the flame? In other words, would twisting the single knob change the amount of air mixed with the propane or am I just going to have to break down and obtain a dual tank kit?
You can do the things you mention with most torches but if you need higher heat output you have to go to an oxy/air/fuel torch.
Look down the page at propane torches. These are a just a few on many propane/mapp torches available.
You might want go to a refrigeration/air conditioning supply store and look at some of what's available.
There are sites on the net that supply just jewelers torches.