As far as exploration goes, it's got a huge procedural map. There are six playable biomes, plus the ocean, with two more biomes eventually, and maybe the ocean. Each biome has mostly the same stuff wherever you find it, but you can find a spot with several close by for easier access to materials, or maybe you're after a nice view. You have to go looking for the bosses and the trader, but there's also a website where you can look up your seed and see the whole map if you're not that patient.

Using dev commands is pretty easy. You can turn on ghost mode so the mobs don't attack unless you do first. There are also a lot of mods that will change all kinds of things. Tweak whatever number you want, craft from containers, plant everything (for making gardens), enhance your building options.

You can alter terrain and it's highly recommended to do so. Mobs can't jump or climb steep cliffs. A simple dry moat around your base will protect it from most of the raids. You can use the same character on different maps, so if you kill the bosses on a different map the raids won't advance on your building map.