First I have to say that I love this version of Budgie. This is great work! I am using the Pocillo theme but the Pixel saver buttons do not match the GTK theme. Is there a way to make it use the theme buttons?
It is a known issue with the third party developer who created the applet.
It really needs someone to fiddle with the code to fix this.
If you are interested in having a go the github project to fork is this
I did spot an outstanding pull-request upstream which I have now patched the deb package with.
It doesn’t specifically ensure that the buttons match the theme - but it changes the button relief and background and does look much better than now.
Just update as normal, logout and login for the update to be visible.