"I understand that the "perfect" grease for bike bolts is the Parktool grease." Parktool has a great reputation (and often a premium price) but it has no patent that would make every product they make The Best Thing(TM).
There are many good greases for many various manufacturers. There is not much to make wrong with a traditional grease (petroleum jelly), just choose the right viscosity. There are many modern greases with various additives (teflon, ceramic) from many manufacturers.
The main point of a grease is to maintain the surfaces easily separated, screwing and unscrewing possible, prevent rust and bonding of those surfaces. A thread-locker, on the other way mainly joins those surface and will enable firm connection with a smaller torque.
But also, some threads are to be greased and some are to be thread-locked. The manufacturers normally say which is supposed to be used. For example, pedal threads are normally greased, while stem and handlebar bolts are usually thread-locked. Also, bolts on derailleurs are usually thread-locked. Carbon on carbon in seat-tubes usually calls for carbon-paste while metal-on metal seat-tubes normally call for a grease. For shoe cleats you should read the recommendation of your manufacturer. Mine calls for a grease but I would expect a thread-locker to work fine too.
You should use what the manufacturer calls for especially when you are screwing to a certain torque setting. One could over torque the threads when greasing what was supposed to be thread-locked. Or the opposite.