Flash is what the engine speed goes to when you whack the throttle. Different from what you would see power braking.
Loose versus tight is mainly (sorta) dependant on the physical size of the converter. An eleven inch converter can be made to stall as much as an eight inch, but it will be unbelievably sloppy, and undrivable..
It couldn't hurt to check out Hughes tutorial on converters, (especially the stall speed one) on you tube.