It's probably the safest zone as long as you build a canal around your base, or raise the ground around it, to protect from Trolls and the like. Best on a coast, usually there's a number of small islands you can pick from and use, and you can then pickaxe the ground between the island and the mainland in any areas that you can walk, in order to make it deep enough so that things have to swim across to get to you, which is essentially troll prevention and Greys suck at swimming and can easily be sniped in the water with a spear or a harpoon later - so basically nothing will threaten you. You can also raise the walls around the perimeter of your island facing the mainland too, in case things do make it across they still can't get in - strategically leave gaps to funnel enemies, or whatever you want, really. Terrain manipulation is key to a safe base perimeter regardless of where you build and you'll learn this around Black Forest/Bronze Age anyway.

The main reason it's the "safest" is because of the above, and there are no water creatures like Necks that will harass your boats if they spawn near enough to become curious - rare and more of an annoyance than anything else since they are weak, but doesn't exist at all in the Black Forest which kind of puts it above the Meadows, marginally.

The other zones have things that can fly over your walls and such (not to mention no matter where you build, raids exist) and are of course tougher than the Black Forest by default.

In terms of a main base and moving - you will soon unlock something that will circumvent this need. Although Metals will still require "journeys" if you do only have one main base.