I've no idea at all about British illustrators. What is clear from Rebours story is although there was a good bit of travel involved (AFAIK only Europe and the UK) it wasn't particularly well paid, and he wasn't allowed (in Le Cycle magazine at least) to write any of the copy. So he wouldn't have been considered a 'cycling journalist', though without him, they'd have been knackered for print! I reckon he probably did more for the European cycle trade than any magazine ever did. Ideale named a saddle after him! That's not bad going.
Black and white pages were the order of the day in pre 1970, because it was cheap presumably and only front covers or 'specials' plates in the interior were ever in full colour.