Just adding an extra cooler is not good. It will make your transmission run too cool at times. It has to be a fairly complicated upgrade, with a thermostat or some temperature-based flow regulator, for this upgrade project to really become an improvement.

Yes.

It's a common mod people do in easter Europe.

It REALLY helps transmissions on cars like the DCT on EvoX last MUCH longer and work smoother.

Question is too vague, but in most cases, no.

I've had one on almost every car & truck I owned, I don't tow but I did street race alot (70s-80s Chevys), the ones without the cooler had issues. Out of seven vehicles over 23 years only two didn't.

With a cooler even with hard use they made it to around 200,000 miles. I used to launch my 87 Camaro at every street light like I was on the 1/4 mile (open headers drive men to such behavior😄) & it lasted 13 years without a fluid change. Then in 2016 it finally fragged.

Despite my luck, even with a cooler keep on top of the fluid changes & don't mash the gas from dead stops💨