So I'm finding it a little difficult to figure out how I should be powering my setup. I'll have Waveshares IO board here: https://www.amazon.com/gp/product/B08VJBGD1Q/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1 along with the Compute Module 4 Lite (8GB RAM) and I'd like to have the capability of fully powering one of those PoE ports and at least 1 USB port.... plus the Pi of course. So assuming both the PoE and USB device are drawing power at the max, what does that result in? I started reading about voltage, amperage etc and realized I don't want to blow anything up (Pi 4s are rare and very expensive these days) because of my misunderstanding so I tried looking up some power supply calculators but all seem to be for PC desktops. I'm pretty confident that this: https://www.waveshare.com/ord-psu-12v2a-5.5-2.1.htm is enough, but I wanted to check with you Pi folks first. That would provide enough power, right? Please feel free to link any good calculator sites out there as well, already got a nice collection for my new Pi 4 rolling :)
Warning The Raspberry Pi 4 DOES NOT requires a 3.0A minimum - that is a recommendation.
That will not work. The Raspberry Pi 4 requires a 3.0A minimum. Start by adding the worse case current for each or the other hardware devices then add 20% now add the 3A minimum the Pi requires, this gives you a minimum requirement for your power supply. Take into account the loads you add to the board. Your link does not give any information for current or wattage for the Waveshares IO board. Be careful that you use the correct voltages.