3DPrinting

I am getting my first 3D-printer (a Prusa CORE One) this week! I have tons of ideas that I want to get started with, but the most time-sensitive one is to make some self-watering planters for my balcony (so I can have time to grow some greens in the season). I wanted to do this without a 3D-printer last year, but I could never find any cases close to the right dimensions in the stores, and making the separator between the water reservoir and soil from off-the-shelf parts was not so easy with the cases I did find, so I hope I am able to make something functioning with my 3D-printer this year.

But I'm new to this, and I am looking for some advice to where to get started reading up on different concepts that will be relevant to this project. These are the things I am planning to dive into over the next weeks, and I am sure there are plenty of things I have not thought about at all:

1. Splitting and joining 3D-printed objects: The overall base area of the planter is too large for my 3D-printer to do in one go, and I am likely going to need four parts that I need to fuse together. I am thinking there are many "standard" ways of doing this, such as splitting with a jigsaw-puzzle pattern? I am also planning to simply glue to the parts together along the seam, and add an additional layer of glue along the boundary. Which leads to concerns about...

2. Water tightness: I know that making watertight prints is not the easiest thing in the world. The container should be able to contain water without leakage, and I am planning on reading up on all the ways to make the prints themselves as impermeable to water as possible. I am sure there are much to learn in terms of slicer settings here. In addition, I will look into different coatings I can finish it up with, such as a layer of water-proof wood glue. However, the water here will be absorbed by the soil and then by the plant's roots, so this coating should be non-toxic.

3. Material choice: To begin with, I will only have PLA available, but I can get other filaments if needed. There are two immediate concerns I have about this: whether it is food-safe (for the same reason as above) and whether it is suitable for outdoors use. It will not be in direct sunlight, as I will build a wooden case around these 3D-printed containers, but the planters themselves will be, so it could get a little hot during Summer. Any other considerations I need to make?

4. Modelling the parts: I am already familiar with Blender, and planned on using it for the first project. I have FreeCAD installed, but zero experience. The shapes are simple, and I am sure I can draw up something in Blender in no time. But since I want to split them up, and join them ideally as flush as possible, will the models be precise enough? Dimensional precision is the main reason I've heard for using CAD-software over Blender for hobby basis.