Wow, your tank is beautiful. For quite a while I'll be shying away from multiple males in a tank, but it would be a wonderful thing to accomplish.
I currently keep a single female and male together, and even with that I will get comments that inevitably they'll kill eachother. However, my female is very docile, and I introduced them with a lot of monitoring, and finally they've become good betta friends.
It's really all about personality. Some bettas are simply aggressive by nature, while others do well with others. As long as they can always be separated instantly should something happen, and you have medicine on hand of any injured fins that could occur... well, there's not much of a reason not to keep them together.
Most of my experience comes from the internet, to be quite honest. I had two 40 gallon tanks that I maintained with my dad 15 years ago, which we had for about a year. Simple fish, black gravel, blue light.
I got back into the hobby about nine months ago. Started with a 5 gallon, and did what I knew- simple fish, black gravel, blue light.
Then I started reading about plants, and more complicated setups. I learned about gas exchange, so I figured out that I didn't need bubbles (which I hate). I kept reading and learned about the light demands of different kinds of plants, wattages, and light spectrum.
What I learned was that if I kept reading the same info from one website to another, it was probably pretty accurate. After two months, I moved up to a 20 gallon. After a few months of that (and many small successes with plants and fish), I decided to jump in with both feet and spent about 5k on the tank in the photos.
I've done enough homework to know enough of the basics that all I'm learning now is practical truths from my own experiences.
Actually, reading over this post again, maybe I do fit in the "pretty experienced" group, lol.
Well, they absolutely stay away from the top unless they need a breath. It's a pentagon shape, so there are three corners where they can hang at the top without current, and they do use those spots. Most of the time though they hang out at the bottom in plants or rocks.
I have two powerheads pointing up to help move the water and filter out particulates. They get caught in these once in a while and get blown to the top, but they learn quick.