You're welcome.
Go manual with your focus. When using a tripod to take pictures of stationary objects, like corals, you can put the focal plane exactly where you want it. And the width of your focal plane can be varied by your aperture (small f number, big lens opening, less depth of field / larger f number, smaller lens opening, greater depth of field). I'd suggest starting midrange (f8ish) and varying as you see fit.
I hear your historic reluctance to shoot straight on because of flash reflections. The good news is that with a tripod and no flow, you'll be able to use much longer shutterspeeds so you won't need to use a flash generally. Not saying flashes are never useful, just that with a tripod and stationary subjects, one can often get by without one.
Absolutely composition will develop with practice, especially if you're conscious of it. You've already got the biggest tip, avoid center composition. While appropriate for online catalogs of corals, center composition produces generally visually much less interesting images. Composition is about the balance of shapes, space, color and light.
Often choosing to include or exclude the exif info in a final image is as easy as checking or clearing a checkbox in the settings somewhere. There can also be iptc info which is more info for the photographer than image settings.
