Heat gets way more extreme than the Syntakt. Id say even the clean boost on the Heat is stronger than the Syntakts analog drive but I haven’t ever really compared them. But if you want harsher, edgier, Analog distortion the Syntakt isnt as capable in that regard. But even the Saturation and Enhancer give much more character as well.
Syntakt does have the immediacy of being able to automate its filter and other FX parameters directly from its own sequencer. It has the ducking envelope as well where the Analog Heat can be used more like a standard compressor.
With workflow, unless you’re using the AH on the master and are controlling the whole thing with Syntakt I’d probably just multitrack everything out of Syntakt with Overbridge into it’s own lane then use the AH on the sounds I want, and record those passes individually or in a group.
Edit:
I would say it’s worth taking a look at a few distortion plug-ins before using the heat as it can be a bit annoying to have to re-record passes when we know there’s easier ways out there. Saturn 2 is very good, has many of the same controls plus it can be used in a multiband way.