GregTech Community Edition adds its own EU that isn't compatible with any other energy types.

So, this is what I found by looking at their source and the FTB wiki:
Gregtech uses a capability based energy system using their own IEnergyContainer capability.

https://github.com/GregTechCE/GregTech/blob/master/src/main/java/gregtech/api/capability/IEnergyContainer.java
https://github.com/GregTechCE/GregTech/blob/master/src/main/java/gregtech/api/capability/impl/EnergyContainerHandler.java

The FTB Wiki says, GregTech6 doesnt have energy tiers but scales linear. I assume this is the case for Gregtech CE as well.
https://ftb.gamepedia.com/Getting_Started_(GregTech_6)#Electricity

Since I've never played with gregtech, I'd like to know if this means we need a way to limit the amount of power. As I understand it, Gregtech uses 2 values for their power system:

• Voltage: The amount of power
• Amperage: Amount of power packets per tick

This might require either multiple tile entities with different tiers or a configurable GUI to not overflow the network/machine with power (as this can cause explosions).

How do players handle this with only gregtech features? How do you control how much power a machine gets?

You don’t need to control the power. Gregtech have voltages like IC2 meaning if a cable is LV it can run any LV machines no matter how much amps it have

Side note:
1 amp = 1 machine can run perfectly on cable
2 amp = 2 machines can run perfectly on cable
etc

Here’s a discord invite link for Gregtech-CE
https://discord.gg/Tp3yDnE