Is a Canon extender a worthwhile investment?

I’m toying with getting an extender to use with my 70-300mm f4-5.6 lens (on EOS R6 Mk II) and I’d be interested to hear views on the pros and cons in practical terms. I’m aware that there is some loss of image quality as well reduction in aperture size.

How significant have these drawbacks been for people? Does the AF continue to work as expected or is that affected? Is it better to go for the x1.4 or the x2?

Any other observations would be useful too.