VarChars is based on measuring precise string widths. It is better suited to the use of variably spaced fonts, and tends to produce smaller, more pleasing forms, without unwanted space. VarChars is implicit when you use 'Layout form' and is recommended for all new forms. Refer to Form Layout for further information.

FixChars is the old layout mode retained for backwards compatibility with older PML applications, which is based on the use of notional character width to calculate the approximate sizes of textual gadgets and gadget tags.