Santander 123 credit card cash back on TfL??

Davuba

Hi, I travel 5 days/week on national rail and also the underground at peak time from zone 1-4 and use my Santander 123 credit card to tap in and out via contactless. Do I get cash back for my journeys?
Having read the T&Cs I think I would only get cash back if I were to purchase a ticket or top up my oyster with my credit card. Is this correct?
Is it therefore better to,
A) use my oyster and top up with my Santander 123 card
use another credit card to tap in and out - I also have an American Express preferred rewards gold card and also an American Express platinum cashback everyday reward card
C) another option??

I spend £47/week on travel so am looking for the best way to make it economical.

Many thanks