Insteon Integration Confused

I’m currently using ISY (Polisy) with a serial PLM and HA virtual on a mini-PC. I have predominately Insteon devices and a few z-wave. The ISY supports both.
I’d like to eliminate the ISY and do Insteon via a PLM and z-wave via USB Stick, all with HA. Also, eventually go with a ODROID-N2+.

I’m not exactly clear on hooking up the Insteon PLM. I’m assuming you plug the PLM either USB or Serial into the hardware that’s running HA. So, then an Insteon HUB isn’t required but is a HUB desirable? Is there more control or advantages to using an Insteon HUB with HA? I haven’t looked into z-wave yet with a stick so that’s a question for a separate topic. Feel free to chime in if you have any experience.