The annotation is the set of all reference designators. (You know R1, C5, …)
The match method is if kicad uses the annoation or the hidden unique id of symbols and footprints to find which footprint is connected to which symbol.
In v4 it was called by timestamp vs by reference. I have no idea what it was called in v5.0.x. In v5.1.x the options are “keep existing symbol to footprint ascosiation” vs “re ascociate footprints by reference” (The former should work if you did not damage the underlying data structure of your schematic while adding new stuff. You can always try the second option if the first did not give you the correct result.)