It is possible to use more than one currency, but be on the standard of only one. I use USD, Bitcoin and Euro, for instance. If I convert from one to the other, or send or receive payments from "foreign" currencies, that doesn't change the underlying standard.
I am on the Euro standard in Germany and the USD standard when in the US (I have a bank account there), but am slowly transitioning to the Bitcoin Standard.
Zaps have given me some affinity for satoshis, as my base zap amount is always equal to roughly 2¢ in Euros.
27 sats ≈ 2¢
2700 sats ≈ €2
27000 ≈ €20
