Back again with more info! Here's my findings:
- The plugin which caused the title font-size-lock was Hakuen BITMAP FONT plugin. Its something I CANNOT let go of, as its all I have to vectorize text properly (after hand-editing every single letter/special characters, by the square, that I added + a separate file for the outline). However... despite everything, its a non-issue. The size is standardized as I like it already, so ignore this worry.
- The plugin which caused the long-title and description text to be 'eaten out' through the border is Hakuen's MessageActions (you can inspect is as its free). I cannot let go of that one either, as it enables a lot of easy-to-use tricks, which honestly should be default in RMMZ.
PS: Deleted the other reply (exact same) as I had it set to 'reply to another' which made it appear in the middle instead of the end. Its just to prevent confusion and for making it easier to follow to you, me and passerby's.