Any suggestion?
fpGUI interface is not yet complete, Graeme does update it once in a while, but it will require much more contributions to be on par with other mainstream interfaces.
A lot of things have been implemented, though, it's just incomplete.
fpGUI is not a widget set. It is a complete framework. You should not mix frameworks.(although some non-visual things may work).
Certainly for average programmers and beginners it is either/or. Either LCL or fpGUI.
Their architecture is conceptually very different.
He clearly mentioned
interface and
widgetset, in case you're confused, he referred to fpGUI backend for LCL (see the wiki link he posted).