I'd like to grill fresh veggies and fish and have some questions:

Direct or indirect heat? I'm assuming quick direct heat? I saw some
salmon recipes say direct, some say indirect..

Medium or high heat?

And then how long do you usually cook fish, like salmon steak, or
catfish? Around 10 minutes maybe flipping once?

When grilling veggies, I researched on the 'net that you cut them into
small chunks or long wedges about 1/2" size. Then you coat them with,
say, olive oil. Sounds simple and easy enough. Does this apply to most
veggies - carrots, bell peppers, squash, tomatoes..

With veggies I guess you basically cook until tender, easily pierced
with a fork I assume?

Finally, with fish.. salmon steak you could cook directly on the
grill, what about salmon filets? Can you do that on a grill or too
flaky and will fall apart or can you baste them enough with olive oil
for example?