The best presoaks I have used were highly alkaline and designed to be used in bay automatics, or were self serve presoaks that were REALLY cranked up.
Many operators and chemical guys are still nervous about screwing up paint jobs with strong chemical. If that was a problem, I'd be out of business by now.
I'm currently using scotch plaid extreme at about 50-64:1. It has a pleasant scent. It foams and looks great at 90:1, but if you want it to clean well it needs to be run stronger.
As far as heated presoak, if you add air into the system, it's going to remove (absorb, whatever) most of the heat that you paid to put in it. A good strong presoak put on at a decent pressure will do the job without heat.