I've run my boat with fins for 25-years. I just replaced the old vosper system with Wesmar.
First, they do take some engine room space. The hydraulic tank and the hoses do take up some room. Nothing like gyro, but not zero either.
Second, they do require maintenance. Every few years the fins should be pulled and the seals replaced. About $1500 or so added to the haul.
Third, while I have occasionally caught kelp, I have now installed a deflector in front of the fin that should make this tiny issue a none issue.
Third, I have zero concerns about the protrusion. Yes, in theory there is exposure. But in reality the risk is infinitesimal. But if you're the type to buy meteorite insurance, then it might be enough of a concern.
Fourth, even in open ocean conditions, I probably run my fins around 50% of the time though I am a bit of a sissy about choosing wx. And that's on the Pacific. In your intended grounds, would be much less. Fins are ideal - I have been known to turn them on for a ferry wake, then back off. But my boat is heavily ballasted with a very low profile so has a lot of inherent stability. Many boats require fins to be run constantly when underway.
At-anchor. My cruising grounds - pacific coast - is notorious for open roadsted anchorages. Some form of anchor stabilization is highly desired. I prefer flopper stoppers with outrigger poles. I store mine horizontally along the cabin side. They take about 10-mins to deploy and retrieve. They work extremely well and of course take zero power. Best I can tell, your intended cruising grounds would rarely need at-anchor stabilization so you may want to consider flopper stoppers rather than burden your underway stabilization system selection with a rarely deployed use case.
As an aside, sounds like you're trying to displace need for a generator and run off an oversized alternator and LiFePO4 bank. If so, you may want to rethink excluding the generator. The Loop and Bahamas will have heavy use of A/C not just for cooling but to retreat from bugs. But if you're including a generator too, then disregard. Also depends on how well ventilated the boat is. Although increasingly rare, some boats have decent flow-through and are very comfortable without A/C at-anchor as a result.
In closing, I agree that stabilization is a must. Seakeepers seem fine. Both systems (fin or gyro)! are expensive. The reason I will never own a SK is due to power requirements. It's just not how I like to run a boat. Nothing wrong with full-time generator use, just not what I want. I realize you're considering running off main engine alternator which mitigates much of my concern.
Good luck with your build.
1970 Willard 36 Sedan Trawler