Do I always need Photon to get the tiles galleries to work??
Tiled galleries use Photon regardless, that's how the images in them are resized on the fly.
It looks like Photon is slowing down my website. I would like to disable is.
Photon should actually speed up a website since it uses a global CDN. It's possible the issue was local or related to a regional network issue or temporary or something else (it's hard to say without more information). I would recommend checking it again.
You can disable any Jetpack module by clicking Learn More > Disable under the module though.