No, Edge IS an Ignition gateway, that optionally supports an HMI. "Edge of your networks" means geographically scattered.
If you want a machine HMI, just run a client on a touchscreen PLC physically mounted at the machine, connecting to your central gateway. (Preferably a redundant gateway.) With normal licensing, you can run hundreds of Vision clients from a central gateway. (Fewer Perspective clients.)
This topic is specific to machine HMIs:
This topic has more general comparisons:
This topic discusses considerations when coming from another SCADA platform:
This topic covers some server sizing considerations: