Here is what the project looks like when I preview it (This is using a lower layout scale so you can see the whole island)
AS you can see, everything on the screenshot you see are individual objects around 15x15 pixels big.
These are my events
There aren't many collision checks and very few every ticks. I feel like it might be the amount of objects I have. The only reason I wouldn't go to tilemap for my tiles is because objects can help me give the affect that sand or water is lower (by a pixel) than normal land as you can see in this screen shot.
The resolution of my images are very small as you can see, so I am not convinced it is the resolution of the sprites. Also, I do believe I have events that prevent any tiles from spawning on top of each other. I hope all of this helps. Thanks