I'd like to make 'damascus' from two types of stainless steel (so that the final product also has anti-corrosion properties).
Which steels will allow you to maintain relatively good contrast without the need for deep etching?

Have you made regular damascus before? Do you have experience with Extremely toxic flux? How do you expect the steels to show differences without etching? Or  are you just worried about etched topography?

try starting D2 and 304 and then 304 and 440C

Look up "Fluorine and fluoride toxicity and precautions. It is an extremely reactive group of chemical compounds, so reactive you are not supposed to use fluoride tooth paste if your water is fluoridated. 

Frosty The Lucky.