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Hi Bill,
I think you've got it right for the most part. I think of 5200 as an adhesive, not a sealant (although it does seal too of course). My most unpleasant encounter with 5200 was a boatyard using it to seal the bolt holes of my motor mount to the transom. It squeezed out between the mounting plate and the transom, and ripped off a bunch of gel coat when I removed the motor. I swore I would never use it again. That being said, I just used it a couple of days ago to bond a t-nut to a stripped out wood face.

I've never used 4200. It seems to be an intermediate step along the adhesive/sealant curve.

I've used 3 varieties of BoatLife: Life Seal, Life-Calk, and Silicon Rubber. Life Seal is an excellent sealant which cures overnight and has modest adhesive properties. I use this to seal hull penetrations almost exclusively. My technique is to countersink a bit about the hole, clean, and fill with Life Seal, letting it cure overnight. This forms a plug which will not get dragged in or out of the hole The next day I flatten the dollop with a razor/knife and reapply a small amount of fresh sealant on top. I then drive my fastener into the hole. This has both the hole and the threads well sealed. I spoke with the founder of the company, who offered that the most common error in sealing fasteners is applying too much force and squeezing most of the sealant away from the site. The countersinking keeps that from happening.
I used Life Seal to seal the fuel tank cover back to the deck.

I used Life-Calk to join the gunwale boards on my 1985 Outrage 18. It is very stretchy and will accommodate significant wood movement. The downside is it takes a long time to cure.

My use of the Silicon rubber product was in rebuilding a modified grommet for cables into my outboard. It bonded well to the existing grommet material, and filled gaps where I had ground out excess stock.

Dennis