<--- started using 5200 in 1974 (same age as my boat), following industry standards. Have NEVER had a problem.
Sikaflex - excellent for acrylics. The city of Houston is held together with Sikaflex (see their literature). I don't like how one has to work with it (fairing, shaping, shifting part during installation, etc.) and so I no longer use it.
LifeSeal is a silicone/polyurethane hybrid, excellent for Plexiglass and plastics. You will never paint near it again, however (same as silicone). Install only as the last step in building/restoring the boat.
4200 is a weaker compound than 5200 meant for deck hardware which may be, at some point, removed. I classify 4200, 4000UV, 5200, 5200FC as essentially the same thing, because they are. For strength & durability I would use only actual 5200 under the waterline. Imagine if you were to hit something and it dislodged something you'd installed with something weaker. It could happen. 5200's not expensive enough to not just use the very best adhesive available.
Thiakol is good for bedding bronze seacocks and metal parts to fiberglass or to wood. It seeps into wood pores and holds well; but it can fail especially in cold temperatures (Space Shuttle disaster). It's what was used for nearly everything before 5200 (wood/fiberglass-composite era). I've found that 5200 is so strong it should NOT be used with wood along the grain line (though it bonds really well) because it will flex less than the wood does in wide temperature changes (result: split planks). Thiakol gives more than the wood, but it continues to hold along the grain line. It is still used between planks on teak decks (such as on my bridge deck).
I'm just advising what the boatbuilding industry historically (over a long period of time right up till today) does, not what boatyard 'experts' say from anecdotal evidence. I am, in fact, an expert. I share what I know because I care about people and about making their boats better.
Not sure if there are other lifelong professional boatbuilders or designers here. If so I'd be happy to hear from them!