Rules:

8 deck
S17
D9 (actually D8, but that's irrelevant)
DAS
Suited BJ pays 2:1
Five card 21 (not just any five-card non-busted hand) pays 2:1

This is a game in the Betfair "zero margin" series.

1) what is the precise return with perfect play? The claim is 100% exactly, but I can find no corroboration for this.

2) Does the "five card 21 pays 2:1" necessitate any strategy variations? My feeling is that it doesn't but would like confirmation. It is EXACTLY 21 required, and only five cards, not six or more or any five-card charlie.