For me, RBL World Safari always charges at par with Google/Visa conversion with 0 charges.
Checked my transaction and saved screenshots. In April, I used it for US$ 87.08 on Amazon.com. That time, google showed US$ 87.08 = 7260.76 @83.38.
And I was charged Rs.7257.03 @83.34 by RBL bank.
Same goes with Fi Money (Federal) Debit card (they refund markup fee few days later).
Have used both these cards on websites while being India, in Dubai and Indonesia (got ALL my USD back from Indonesia) in last one year. Have never been charged more than google/visa conversion rate.
For me, using SBI cashback gives 0.87% cashback (5% - 4.13%) and one is not 100% sure if he/she will get 5% cashback or not (excluded MCC codes). So, I am happy with RBL World Safari CC and/or Fi Money DC.