The published trial records (which anyone investigating the affair might be expected to have read) gives Cadoudal's height as 1.63m, which works out at 5ft 4ins (imperial).
Witnesses described him as fat and big-bellied.
I don't remember red hair being mentioned, I will go back and have another look.
It would seem that the writers you quote have more in common with each other than with the primary sources.
Susan, the reference to cinq pieds et 3-4 pouces can be found in the description in the Police Secret 'wanted' leaflet circulated in 1804. My understanding is that the pre-metric measurement was equivalent to 5'.3"-5'.4.'' Curiously, Andrew Roberts describes Cadoudal as "tall and burly."
'Georges' seems to have been notoriously red-headed; not an ideal feature for a dissident living undercover.
'SIGNALEMENS. De plusieurs individus dont la recherche et l’arrestation sont ordonnés par le Gouvernement'
N°1er CADOUDAL (Georges), dit Larive, dit Masson, né aux environs de Vannes, ancien chef de rebelles, taille de 5 pieds 3 à 4 pouces, extrêmement puissant, très-ventru ; beau teint, frais, blanc et coloré, peau très-unie et lisse, point de taches, yeux gris, point expressifs, cheveu chatain clair, assez fournis, a la Titus, coupé tres courts, ne frisant point, excepté devants, ou ils sont plus longs..[eyebrows] [ears] ...nez applati du haut, assez large du bas, bouche bien, dents trés blanches »..etc.etc.
I read elsewhere that these details were provided initially by the doctor Querelle, who landed with Cadoudal in August 1803 and was arrested early in 1804. I haven't followed that up but it seems possible.