To clarify, this kind of depends on the race. Daniel is a reserve driver for Red Bull (also Alpha Tauri), primarily at the races he’s attending (of which there are eight, I believe). Lawson is presumably the default at the other races, but if Ricciardo is available they could well choose him instead.

But yeah, as Lawson and Ricciardo are shared with Alpha Tauri, they could also, for example, ask Yuki to drive the Red Bull and put, say, Lawson in the AT.