If a ship has a strain and a stress token would a blue move take off both of them on the same turn or just one at the players choice?

Both.

Hmmm seems a tad powerful and makes strain less of a disadvantage. Guess depends on the pilots initiative.

2 hours ago, Fudwicket said:

Hmmm seems a tad powerful and makes strain less of a disadvantage. Guess depends on the pilots initiative.

Thats like saying performing an ion maneuver (which is blue) to clear both the ion tokens and a stress is a tad powerful.

Stress and strain are separate effects that do different things, and FFG has stated they are trying to reduce token stacking, even the bad ones. Thats why Jam tokens go away at the end phase now.