Nice video and opinions.
I am not taking either side of this hot or cold topic.
I do want to pose some questions.
This is my two cents.
Won't the water in the pump heat up to a point where the thrmostat pops open and the hot water of the pump will start mixing with the cold water of the water jacket?
Water has a great capacity to hold heat.
And the entire mass of water that is in contact will try to reach equalibrium.
So I am sure the 3/4" will work just may take time and make have some lower temp threshhold where losses to the metal and outside world null the wattage of the heater.
You would also want your heat source as low on the engine so that as the water heated it would rise and mix with the cold. adding from the top may stratify the temp layers.
Also some portion of the heat leaving the radiator will radiate on the engine block and help to heat.
The 3.4" method might also be better for those looking for a less mechanically involved method. Screw out and in. Frost plugs are more involved and more invasive if they go wrong. I have done a handfull on school buses with more woom around the block.
A lot more complicated set of thermal systems than just what you covered.