IPL can be effective is done properly and on a good machine, as mentioned though the problem is many people purchase an IPL for skin treatments, then realize oh we can do hair removal too might as well do it. It’s impossible to say what settings are required because each machine is different.
IPL blasts every colour of the spectrum vs just one like a laser. Filters are applied to the IPL to filter out various wavelengths and to focus just on the best one for hair removal. The wavelengths are optimal for hair removal as it’s not designed for this purpose specifically.
It will seem like it’s worked but then in a few months the hair just comes back because it’s not as powerful as a true laser, so it only stuns the hair and doesn’t kill it.
Yag doesn’t have the highest risk of scarring, it’s one of the safest lasers as it can even treat black skin. I don’t know where you heard that they’re more painful, I use both a yag and alexandrite they feel identical. I’ve had the best results on my face by using a yag. IPL is not good!