Acrylic form is a part of fluent design and I thought to make a property which will include most these parts.
After acrylic form I was planning to add more sub-properties there, but now I see that you are right, “SystemBlur” will be better. Other new properties will not be included in this property, they will be placed separately and it will be better for developer, seems, more intuitive.
Acrylic blur used if Mode sub-property is “fmAcrylicBlurBehind”. It’s supported in Windows 10 only, otherwise will be used old fmBlurBehind mode.