Two ways of sending the appropriate energy to the appropriate drivers.
1) "Passive":- a single power stage amplifies full range signal, and divides the output power by frequency band between the different loudspeaker chassis. This separation is done with high power components, inductors and capacitors (which in theory are high current devices, as no power is dissipated in them, but theory doesn't always come up with it) but often resistors to match the efficiency of different drivers and get the impedance somewhere near constant with frequency, or
2) "Active", where each loudspeaker (or group of loudspeakers within a frequency band; in your example, it wouldn't be worth separate amplifiers for the two eight inch if they were aimed in the same direction) has its own power amplifier and the separation of frequency bands is done using active components at line level. The advantages of the former are the simplicity of the wiring and the need for only one power amp per cabinet, which means a standard HiFi set up can drive them. The advantages of the latter are flexibility: frequencies and rolloffs for different bands don't need to be mirror images, phase angles can be tweaked, frequencies changed and sensitivities adjusted at the touch of a switch or turn of a potentiometer, without requiring rewinding inductors or soldering in new value components. You can even introduce specific equalisation for particular drivers. Much more fun for a development set up.
The downside, unless you are building the power amps into the cabinet, is a veritable spider's web of cables, screened and unscreened, a line level input and multiple power amps. And the possibility of running the wrong signal into the wrong driver.
Passive crossovers can be bought ready made for existing driver compliments, and occasionally modified for others but I suspect your "three tweeters – different" is going to require some custom design. Similarly electronic crossovers can be bought, or built, digital or analogue, for quite reasonable sums, but show a tendency to be preprepared for standardised systems; a low to mid frequency selectable, but automatically the same for the two drivers, and automatically the same order of filter, and again, a mid to high.
If all your tweeters have the same recommended low cutoff, this would be fine for you; three different HF power amps, relatively low power, each one its own volume control and perhaps equaliser, but if two of them were 3kHz recommended crossover and the third a 5k hypertweeter you might have difficulties without DIY.
Is that clear? No, it probably isn't. And it's only the first stage of getting those units cooperating.