Overbridge basically just turns the unit into a VST plugin. It sends the audio to and from the unit over USB while not messing with your audio interfaces connections (technically you can only have one audio interface working on windows at a time but some drivers support multiple, but the results are varied).
But anyways, if you use Overbridge you get a much better visual representation. And yeah it does have side chaining you just filter out the bands you don’t want to side chain, but that won’t stop the device from coloring the whole signal if it’s on the master. So splitting the master signal into two (on ableton using an FX rack) you can put a HP filter before the Heat on one lane so you’re only effecting above a certain band. Or like @DaveMech mentioned use the Heats HP filter to cut out the low end and adjust the amount with the mix knob.