A raised garden does not have to be enclosed, it can be open with just the soil hilled up. It is the easiest and least expensive raised bed to make. Most people do build raised beds out of wood, concrete, bricks , or stones and it is more like a giant container garden.
The reason I like raised beds was because I started off with very compacted clay soil. I built mine out of dry laid tile because it required very little skill. and 2 tiles high was 16 inches deep. I could sit on the side of the bed to work it and at 16 inches, I could grow some root plants like daikon. I don't plant too many carrots because it is not that easy for me to grow and it is cheap to buy. I grow a lot of herbs since they are expensive to buy, taste better fresh, and the Asian herbs are not always that easy to find. I have pandan, ginger, turmeric, Jamaican oregano, lemon grass, rakkyo, garlic chives, and green onions. I aslo have citrus trees, tomatoes, eggplant, and peppers in pots.
In my community garden, I do in ground planting. I have pathways between the beds but the beds are not raised because the soil is soft and well drained.
Happy gardening in Hawaii. Gardens are where people grow.