Hi, I have a few comments and I hope they are somehow helpful.
1. You can connect more than one fan set to a powerbank. Most of them can provide at least 1 A of current and each set requires approximately 0,3 A (if I remember correctly). The Velleman kit runs on 3 AA batteries, which sums up to 4,5 V. That's why it should also work with 5 V from a powerbank, but I guess you'll need to check if the voltage is stable enough and doesn't cause any interference. I once tried it too, to replace the batteries with a USB plug, but I can't remember the outcome. EL-wires need an inverter to boost the voltage, if you use the correct one, you can connect it to a powerbank, too (but I guess you don't get ready made sets with USB, so modifications are necessary). To achieve an illumination all around your visor you can use more than one LED light kit. One of the ones I offer, needs about 0,3 A when powered via USB. Let's say you'll need 3 for the whole visor, that's 0,9 A in total. All of the devices summed up will need more than 1,5 A so you'll need to check if your powerbank will be able to handle that output. If it doesn't have enough USB ports you can use a splitter cable or USB hub. Keep in mind that you'll have a lot of current draw and a powerbank with only 2000 mAh will last for about one hour.
2. You'll need to place the microphones outside of the helmet or at the bottom edge, for that . I use the set in combination with over ear headphones, which I mounted inside the helmet.
3. This is my personal opinion, but I tried EL-wire once and it was very disappointing. It was too dark and the inverter made a loud buzzing noise, which drove me crazy. But I can't confirm, that it got hot.