A little new to using BA Avios to book on AS.

I am looking to book a trip from YYC to SEA. I see that the AS booking site shows award availability for 20k reward seats which I understand are the same seats they make available for partner reward bookings. Two questions:

1) I assume it is not a concern that these same seats DO NOT show up on American Airlines??
2) Is the taxes, additional fees that is shown on AS the amount I will pay when I book through BAEC?

Thanks in advance.