I know you can use pink Himalayan salt for cooking, but I'm wondering if you can use it directly on food after it has been cooked, can you put it on steak or fries after they're cooked, as you would normal table salt?
Yes, you can, and this the way you are most likely to exsperience the textural difference of this type of salt; most people cannot detect any flavor difference for various mineralized or natural salts under test conditions, but this is the manner it is most likely to make a perceptible difference in flavor.
Of course you can use it as table salt ... but I don't like big crystals so I use it a bit milled
Himalayan Pink salt has TRACE elements in it so it's quite possible that you won't be able to tell the difference just by tasting. However, it's a bit pink and if you dissolve copious amounts of salt in water you may see a bit of colored residue (on standing).