Oversized card numbering seems to mimic the Collector Box standard card numbering.
It appears the Oversized card numbering order matches the Collector Box Standard Card ... so if player is OTCSP-1 then they are also CTC-1. I am uncertain is if all player in the 25 card set has a SP Variation Oversized AND a Base Oversized... or only one. Anecdotally it seems each player might has a base and a SP Photo Variation Oversized.
This is what I have oversized
OTCSP-1 - Mike Trout
OTCSP-3 - Aaron Judge
OTCSP-4 - Acuna Jr.
OTC-5 - Rutschman RC
OTC-6 - Pete Alonso
OTC-8 - Juan Soto
OTC-9 - Julio Rodriguez CUP
OTC-19 - Jordan Walker RC
This is what I pulled from Collectors Box Cards Set
CTC-2 - Ohtani
CTC-4 - Acuna Jr (photo is different than SP oversized)
CTC-6 - Pete Alonso (same pic as base oversized)
CTC-9 - Julio Rodriguez CUP (same pic as base oversized)
CTC-10 - Gunnar Henderson RC
CTC-11 - Mookie Betts
CTC-13 - Yordan Alvarez
CTC- 20 Mastaka Yoshida RC
I don't have anywhere near a set on the Flagship cards, tons of dupes of certain players. Really dragging to go through them because its kinda PITA and Topps should have listed this set checklist already. By the time I do it I'm sure they'll list it. I dont mind do the oversized because there's fewer and Topps seems to never list those in a checklist.