I've never used Miller Microplex so I cannot comment on that product one way or the other.
KNO3, KH2PO4, and Plantex CSM+B are what I use. I also dose a little Seachem Equilibrium after a big water change and I dose Fe every other day, 3 ml per 50 gallons.
The Equilibrium and Fe are what I have added based on trial and observation. They may not be needed by everyone. I have no test kits and no idea what any of my levels are. I just watch the plants. The KNO3, KH2PO4, and some micronutrient mixture are the basic building blocks of the fert routine, and those three are what you need.
The set you linked to is exactly the macro and micromix I use, except it has K2SO4 which I do not use.
Yes...those three would cover the basics.
As far as when to dose, the EI method is a general method. It isn't written in stone and can be adapted to specific needs. If using EI, you start off dosing macro every "even" day and micro every "odd" day, then go from there. By dosing something each day, you develop a routine and are less likely to forget to dose, or get confused.
I have a high light, pressured CO2 tank. I dose Equilibrium right after a water change. I dose both macro powders and the micromix powder directly into the tank on even days and I dose Fe on off days. This works for my particular setup. You want to have consistent nutrient levels. You don't want them to ever drop too low. Regular dosing prevents "bottoming out" of anything.
Underdosing is more dangerous to plant health than overdosing. You want to overdose, slightly. This way, you are sure there are no low levels of any particular nutrient - this prevents the plants from having a limiting factor that stops or reduces their growth. You want the plants to have the fuel to use up all the light and carbon you are giving them. If something stops the plants from doing this, it opens the door for algae to set up shop.
My advice is use the ferts you were looking at getting, dose using the EI method and recommended levels, and then watch the plants. You can tweak something here or there as needed as you get to know your plants better. If you want to limit the speed of the plant growth, do it by reducing the light, not the Co2 or nutrients. The light is the engine.
I don't have experience with the AH Supply kits or much recent experience with DIY CO2 (many years ago), so I cannot be sure if you will have issues with too much light for DIY CO2 to keep up with. Someone with more experience with setups similar to yours can comment on that. No matter what nutrients you dose, if the light is too far ahead of the CO2, you will get algae. I'm not saying that is the case with your setup, but you should ask.
