I totally agree. I only played around with the idea of toggle buttons to see if this is something useful. Btw toggle buttons are only 6 lines of code so we can drop them immediately xD.
-1 on the buttons-for-checkboxes. Too easy to confuse with other buttons that are not togglable.
Toggle buttons are great and will reduce the space needed if they are icons with tool tip text, but I think we should stick with checkboxes for now , because then they are self explanatory. I also agree with what Cory said.
I’m also not sure about @mwestphal comment about the precision of the numbers.
Look at this behavior of ParaView
As you can see, the precision of the line wdiget changed when focus is applied to it.