Jany and Menzel are good, but `a dedicated SYW group` falls WAY outside my definition of a good source.
As for IR Nr 54: I quote from the Prussian Stammliste of 1806:
`This regiment was raised in 1773. The officers came partially from the army, partially from foreign service. A cadre of NCOs war drawn from the Magdeburg Inspectorate; the men came from regiments along the border, as well as from Prussia, Silesia and Westphalia and foreign recruits.`
IRNr 48 was raised as a fusilier regiment in 1756 by converting a garrison battalion to the new role.
IR Nr 43 was founded as an infantry regiment in 1741, based on the town guard of Breslau; in 1744 it was converted to a fusilier regiment.
The Stammliste shows which infantry regiments were `infantry` (musketiers) and which were fusiliers.
The Stammliste also says of IR Nr 32, that it was replenished with men from one of the ex-Saxon regiments after the 7YW.
So, Jany and the official Prussian Stammliste agree on these details. Maybe Duffy slipped up or was mis-informed about fusilier regiments. We can see that not all the regiments raised by F t G were fusiliers. That generalisation just is not borne out by the reliable sources.