Just a small recap to scratch the surface.....
You don't need a heated plate. Start off with ingredients at room temperature. It is possible to over-heat just from friction alone.
If your stir bar is not spinning properly, try a (several) different size. Use a lab grade beaker or flask. If your stir bar spins out, your rpm's are too high, and don't expect the stir bar to begin spinning on low settings......crank it up then turn it down.
Although it's possible, it is rare that your mag-mixer is not strong enough for a 115ml batch of 70VG/30PG, but I suggest a minimum of SH-2, higher is better especially for longevity.[life of equipment]
When choosing a magnetic stirrer, it is a better rule of thumb to have one that is 0-1200rpm or 0-1500rpm that states a 5L capacity.......than one with 0-2000rpm or 0-2400 rpm with 5L capacity. The latter will almost always have a lesser motor and magnet.
Remember capacity ratings are 99.9% based on liquid like water or similar viscosity. [unless specified]
The best universal and economic stir bars are octagonal shape, and slightly better are the egg shape, also called olive shape. You still need many sizes, at least to find out what works best in your situation, or situations.....as you make different batch sizes, %'s, equipment, etc.
A stir bar retriever rod (easily found on Amazon) will make your mixing so much easier.......and much less messy.
You DO NOT NEED a vortex !!!!!!!!!!!!!!!! Just an LED flashlight [and an IR themometer].
God bless you.