Anything that
isn't after the amp's transformer and before the speaker(s) is not truly going to be what an attenuator is intended to be (get the amp's power section working heavy while bringing down the volume level). Yes, there are other ways of managing volume but they're actually not going to trick the amp into pushing its power section into breakup:
Anything before the amp is just a boost (or an un-boost) pedal
Anything in the amp's loop (these are not uncommon) is not an attenuator, but simply a "post" volume knob for the preamp no more/no less
Some examples of
true attenuators of which I'm referring to are the Aracom units, Dr. Z Brake Lite/Air Brake, Rivera Rock Crusher, Scumback DBL, Weber MASS, etc. (there's a lot more, and I've used several of them). There are also some more modern/hi-tech units that re-amp the signal and do even more fancy tricks, like the UA Ox and some products by Suhr, Boss, and others.
But as much as I can say which is a "true attenuator" and what isn't, the bottom line is truly this--if you can get your amazing dream-sound/tone coming out of your setup at a volume that is manageable for you, then go with it. For instance, I've used attenuators at times, I've used amps with Master Volumes, and I've used pedals into clean amps. Each one of those, in different ways, have produced some killer tones (and many bad tones along the way); but here is no "right way" anymore.
Attenuators can get expensive real quick, though--if going that route, I've been satisfied on the less-expensive side with practically any of the Weber products, the Dr. Z Brake Lite, and (for low-wattage amps) the Swart Night Light Jr. to name a few. Nowadays though, I'm not using any--it's more just pedals into clean or semi-clean amps, and/or the built-in (but true pre-speaker) attenuators in my Carr amps.