There is no real differences between Headmasters & Titan Masters as they are pretty much the same thing at the end of the day, robots that transform into heads and combine with larger bodies, with Fort Max & Scorponok being bots who pretty much double up on the basic idea to become even larger bots, so any confusion you have, is just down to the marketing and the gap of some twenty plus years between them!
To be fair there kinda is.
IDW established that each of the Thirteen had a Titanmaster in their "court" who could control Titans. And Hasbro's own marketing material made reference to Titanmasters maintaining and/or powering Titans in some way. I'm sure the Machinema show had something in it but I didn't watch it on account of the Combiner Wars show being trash.
Both toy marketing material and fiction seemed to alternate on whether or not they were American style (main body and head being separate characters) or Japanese style (head is the character body is a lifeless mech) Headmasters but there was at least a token effort to work in some connection to Titans.
Plus the whole cityspeaker concept.
Just Emissary. No others.
He was voiced by Jason David Frank?!?!?!
What a weird but awesome voice cast to waste on a Machinema series
More like Mach-enema, amirite?!?!
It was great when Soundwave and his cassette army did it, and it's never gotten old since.