Pixelmator 2.0 Features
How to center horizontally / vertically for text: extend the bounding box.
Unfortunately, I couldn't find any way to do this for other items! I am actually surprised I didn't find it very limiting myself. There are several snapping options, but even when activating “Layers” (not active by default), the snapping happens only on edges, not on center (and it is very small, not as easy to manipulate as in the iWork suite, for example).


Tutorial for Inner Shadows on Pixelmator on YouTube (it's a workaround that consists of duplicating layers). Made with / for Pixelmator 1, but I couldn't find more info for Pixelmator 2.

In Pixelmator 2, you can choose which tools you want to add to the toolbar. Unfortunately, the Transform tool is not offered. 
However, as you outlined yourself, the Transform tool is just one keyboard shortcut away. You'll have to resolve to ⌘F.