Hi TY,
(1) That's related to the DPI scaling. The 3ds Max UI rollup hasn't been ported to Qt yet because of maintaining compatibility with previous versions. However, it's just an "aesthetic issue" and it doesn't affect the functionality of the plug-in at all.
(2) X/Y Pixels values are used to adjust the density in procedural maps without modifying the X/Y Units scale. These parameters are locked when using bitmaps, using the number of pixels of the image as the default value.
I hope that helps.
Best regards,