OK. I've been using aperture priority forever. My old micro-four-thirds camera struggles above ISO 1600. Denoising algorithms can help a little, but too much ruins the image.
I usually use auto-focus, but depending on the situation, zone focussing works great and the camera responds faster.
The camera doesn't matter, except when it does. In my case that's low light. I want to photograph a dance competition. That's going to be tough.
Thanks for the info.