As for anything being impromptu, that is a lie. Everything requires practice, rehearsal, set up. The key is to perform in a manner that makes your audience believe that you are just doing something on the spur of the moment. Thus, the best impromptu magic is an illusion.
This really needed repeated. . .
I have several pieces that I rotate that allow me to know what I'm going to do if in an improvisational situation and most all of these "pre-sets" move things towards Muscle Reading in that, for a mentalist, this is the cleanest and easiest thing to move into outside of doing Readings on folks.
Most people confuse "Improvisation" with "Impromptu", the latter meaning that you have nothing but your wits and enough education and experience that allows you to see what is available and how you can exploit it. But even this course of action requires "practice" -- literally putting yourself into such positions and knowing what you can do if called upon when in a coffee shop vs. a coffee house for instance (big difference between the environment at a Starbucks vs. Denny's for an example). But this also means that you have material at the ready that incorporates the things you are regularly surrounded by, be it when in the classroom or someone's home, or when out in the local park, etc. But like I said, you have routines in mind based on each setting well in advance; material you have practiced well ahead of time and especially routines where you borrow items that belong to folk . . . they like that and it makes the magic that much more enchanting (impossible) to their mind.
When it comes to the issue of "Hard Hitting" pieces we have another issue. . . it depends on the performer, their style, confidence and skill level. The trick or effect presented has little to nothing to do with what is "hard hitting" it is just the vehicle that helps you get there. The secret to knocking the public's socks off is YOU and YOUR ABILITY to "sell" the effect . . . to create mystery and enchantment. You can put five magicians side by side doing the same exact material but only one of them will stand out int the public mind as being the "best" and most memorable. We can see this at Magic Competitions when you have the same sort of acts back to back (usually bird acts).
Sadly, there is one other thing that an audience judges us by, something we had a discussion on recently on another forum I belong to, in regards to Colin Keys on AGT -- Looks!
Our society still judges things based on sex appeal; Colin was young and cute and had a very pleasing personality which is what helped escalate him forward. Kevin James who is hands down superior performer and most unique didn't have the cuteness factor to his advantage; Kev is a big man (I don't mean his weight, I mean all the way around Kevin is a big, very commanding dude, but a gentle giant.) We've seen this with other talent on that show and how the strangest, most horrid acts manage to make it into the finals (though rarely winning, except in those music oriented shows). Understand, I'm not saying that a homely looking guy or gal can't make it, that depends on their ability to use their looks to their advantage. . . a slightly different story though a related issue. Just look at how naturally goofy so many comedians are and how they deliberately accentuate things like an odd looking nose or chin or hair, etc.
If you learn how to carry yourself, take command of a given situation and use your physical being you can do a simple French Drop and win people over. It is not the magic you do, it's a combination of things that range from discipline & command to Sex & Sensuality.