I would add that on your right continent, it looks like a plate being pulled apart at the lakes, rather than two plates coming together right below the lakes. Take a look at North America--the Great Lakes and the many small lakes in northern US and in Canada, and up through those many small islands... this is all a result of the continent being ripped apart by tectonic forces.
Note that plates can have several interactions, and they can take place differently on different sections of the plate. It's all driven by currents in the magma below the plates, which act like conveyor belts.
When plates come together, or converge, one will subduct. This creates a subduction zone where plate is being actively destroyed by being forced under another plate, into hot magma. If these two are continental crust, which is much thicker than oceanic crust, it's more likely to form large mountains. Even small islands are likely to scrape off and form mountains from accretion. Oceanic crust will subduct under continental crust.
Subduction zones are hot spots for earthquakes, as well, and notoriously create very large earthquakes, though are often spaced out every several hundred years.
This is in contrast to emergence where new plate is being formed, often in the ocean. See Ring of Fire in the pacific for a classic example. These spots are usually very volcanic, and can create chain islands such as the Aleutian Islands in Alaska.
Hawaii is a bit of a unique case. You'll notice it isn't on a boundary but is smack in teh middle of a plate. There is a hot spot there, where magma melts through the crust because that spot is much hotter than other spots, and it frequently erupts (Hawaii has many active volcanoes that have frequent smaller eruptions) and while the crust travels as it subducts and emerges, the hot spot does not move. The arc of the island chains is created by very large eruptions of this spot over time. See also Yellowstone supervolcano. This is the same sort of hot spot which erupts in different spots on the plate as it travels over the magma hot spot. If you look at eruptions over time, it has the same pattern. This phenomenon, at least when I last researched it, isn't well understood, but is very interesting in my opinion.
Some of your islands in the middle of the ocean are like this. I think it's fine, considering not much is known about this phenomenon, I don't think it's a problem to have many hot spots.
In regards more to your map vs just info dumping, I'm not an expert on this, just know a bit, but I would say it might make more sense for some of the oceanic boundaries to either be up against the crust, or out in the middle of the ocean (two oceanic plates). Look at Earth's tectonic plates, yes there are some places where a boundary is kind of by a coast but a little bit farther, these are all approaching becoming an oceanic-subducting-under-crust situation. See Japan on a map, this is getting scooted towards China and will eventually just be accreted mountains. If you have a strange space like two oceanic crusts really close to a continent, it might have more of a story.
Finally, I think your crescent island would be best created by a landmass ripped apart, and warped a bit over time, trending to be pulled apart generally in every direction.