I made the experience that too high a cooling substantially decreases layer adhesion even at raised temperatures. Raising cooling to counteract overhangs and then raising temperature to restore layer adhesion in my opinion is a rabbit hole that ultimately leads to worse prints.
I measured layer adhesion of several PETG brands at different print settings semi scientifically in this thread.
It shows that Bambu PETG just is a very odd make that should be printed slow to work at all. Even then I have problems with print quality (e.g. loose strands). All other brands I tried worked great at 240°C with 20% cooling and even resulted in nice prints at 300 mm/s with some reduction in layer adhesion. Increasing cooling instantly crippled layer adhesion. I still should do a few tests at raised temperatures, but the few I did, are sufficient for me to say that temperature can’t compensate the downsides of high cooling.
So I state that cooling is the biggest enemy for PETG strength and it is better to improve overhangs with whatever other measures you have available.
This is not my discovery but what I learned from others and just confirmed in my tests.