With manual ISO, Tv or Av actually does not matter. Wether you're in Tv or Av, turning the e-dial will influence both aperture and shutter speed. Look in your viewfinder and you'll see it; so with Av you can still do Tv
With auto iso it is different as the camera can influence 2 parameters (of the 3) but I don't like to use it as
I don't know when the camera changes the ISO.
I use Av close to 100% of the time (leftover from the film days I guess) and keep an eye on shutterspeed if necessary. The rest is M when using flash.