Hi,
so far, I cannot make a real benefit by using the toucher within Sparkle…
It would be great to have a direct preview, instead of an up popping window on the screen that needs to be confirmed before seeing the preview…
And it would be really handy, to have those move to “background” and “foreground” functions appearing on the tuchbar! 
Thank you!
For previewing, what I do is I keep the preview window open in Safari. Whenever I make a change in Sparkle, I then press Command-Tab (⌘-Tab) to switch quickly between Sparkle and Safari. The preview window in Safari gets updated instantaneously.
As @habboud said, the preview in Safari gets updated immediately. You just have to set it up once and switch with ⌘-Tab.
I sometimes use my iPad as a “preview device” for Sparkle, so I have it on a separate screen.
Some apps allow to customise the touch bar. I don’t know if this is possible with Sparkle, my MacBook Pro is one without touch bar, so I can’t test it myself: