The sizes in the theme are not changed and the theme should look the same way with both versions. Please note that we have introduced a HDPI support in Q2 2017 and I believe that this is causing the disturbed layout.
In order to test this, you can disable the DPI scaling by setting the following property in your main form:
RadControl.EnableDpiScaling = false;
Detailed information about this is available here:
I hope this will be useful.
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