Hey I'm not good at it, but let me have a stab. (Sorry for stating the obvious if you already know...)
Firstly, there are many types of freestyle. I personally define freestyle as anything whatsoever that is not simple back-and-fro saiing.
Bestest freestyle to me is jumping waves, loops and all that comes with it. But it requires very specific conditions: cross-shore, strong wind, waves, etc. That's why 90% of all wavejumping clips comes from .1% of the earth: Hawaii.
Then there is the flatwater, fair-to-high wind freestyle. You must have seen this, for instance Soltysiak in this thread. (We couldn't get the guy out in lighter winds at an event a few months ago, prefers his brand of sailing)
What you have on them's vids is more flatwater and referred to as lightwind. Not sure I agree with either names: I've seen clips where they do pretty much the same with stronger winds. Pous Bonaire being ocean-side, it can get wavy out there, only the very shore is fairly flat. Cape Hatteras, for instance, lends itself more to that definition, even though much less glamourous (not tropical).
All kinds of freestyle have their own equipment and requirements. For "lightwind" freestyle as you see on the vid, and not that I can do it all, then I personally find the shorter the boom the better. Somewhat underpowered is good for more control, and the idea is not speed if you do these things. No footstraps in the way please. Boards: almost anything goes, a bit of extra floatability is nice, but no biggie. I like stability provided by daggers, but just absolutely hate the knobs. I often have modified boards in the past for that - remove da knob. I also find I take time to refine moves on a new board, so stick with the same freestyle board for a season, if possible.
VERY IMPORTANT: nice clean morning on-shore breeze makes it easier. Also important: fairly low boom for lower weight. No harness lines - gets in the way.
Like them, I also like to do it in shallow waters on a sandy beach. Reason is that falling is less of an issue, and just because you don't mind falling, then you fall less and moves work much, much better. In fact on a floater, when am in shallow waters, I removed the uphaul. Problem is that you get lazy when sailing in the shallows, and my same freestyle suffers when I go way out after a while.
I have no issue with sailing around people, I think it's fun and usually people like it. Gives citizens a cheap thrill. Wouldn't do it on a swimming-only beach, that's all. Anyways the key to learning moves is never to sail more than 100 meters before the next move, and restrict the area of sailing to very few 100 meters, so you can freestyle into-out-of transitions of the time. Best way to learn. (I learned on a very small pond at an inland uni town - everyone had super-gybes, and nearly all could freestyle there.) Worst you can do for your freestyle is sail on a tack for an hour before trying something.
One personal note: I find there are few boards tricks on them's clips. Railrides and Everoles - it can be done on some of them's board fairly easily, would add a lot to the routines. Damaging for the boards though, probably be the reason they don't.
I am short of equipement lately, I have nothing worthy to sail until I acquire again. So I have recently volunteered at a local club so I can borrow their various SBs models and railride them all - will try to post clips on the SBs web site. (Danger to their equipment, but they don't know yet...)
If, as I, you live in a less glamourous spot (inland, rivers), you can get an old Windsurfer at a garage sale and fart around in 8-14 knot winds. It's a good way to get the feel for mid-size flatwater freestyle and keep in shape. Recommended. In lesser winds, doing that is also better than sitting on the beach and bitching, which is a fair proportion of sailors in thems parts. However be warned that 80s rigs are near-impossible to handle for freestyle.
Now you can go and try things and spend your entire windsurfing time in the water like me. I forgot: the learning sequence is most important. Too many try difficult moves at first, then just give up. Too bad, not a good reason. Start simple gybes and tacks, eventually duck tacks, good waterstarts, board 360s in light winds, back-to-sail, front-to-back, etc. Throwing the sail around, railrides, etc.: dead last.
Cheers.
