The HP gauge consists of two parts: the fill gauge and the BG gauge. You just need to adjust the X and Y coordinates and enter the values until they align perfectly to your liking.
Yeah, that's a default engine behavior. When you're using the plugin, it updates data in real-time, which can be quite annoying. I'm looking for a way to fix it, but it's a built-in notification in MZ, MV doesn't have this issue.