I recommend to consult volume I of
Alombert et Colin, La Campagne de 1805 en Allemagne, pp. 391 - 408 about the organisation of the Guard, it will provide some good insight.
https://gallica.bnf.fr/ark:/12148/bpt6k873004n/f403.image
also browse
https://gallica.bnf.fr/ark:/12148/bpt6k873002w/f1.image