What's best practice for creating and setting Terrain Textures?

I am a beginner, therefore would like to create games with medium resolutions but at the same time not extremely high graphics. Just graphics that would be good to start with. I am looking for just that right medium.

Question: Say, I have a 2048x2048 Terrain. Then I go and make my own 512x512 .psd texture files… Is my best bet for accurate in-game graphics to set the size to 512 x 512 when painting my terrain?

I also would like to know if you can import the textures in a different format then .psd. I find it interesting that Unity can make the .psd into a useable graphic.

AFAIK, the tile size for terrain is unit-less, meaning you can just set it to whatever looks good, and the exact numbers mean nothing. You can easily change them and see it immediately (don’t even need to click Apply.)

The biggest trick in Unity (or any decent terrain engine) is the ability to arbitrarily blend in 2+ textures, which involves artistic skill. Sure, you can paint a road through some grass, and the engine will give a fuzzy grass/road border to make it look better. But you can also work in grass2 and grass3 into a field or grass1. Not just grass1 next to grass2, but an entire patch where grass2 fades in and out over grass1. You can make some really interesting areas using even 128x128 textures.

Unity also allows you to make a detail texture, by setting the tile size really low (can use fractions) and lightly brushing it in. Can even make a texture be its own detail texture.

The main trick, which isn’t obvious, is that the 0-100 opacity scale is messed up. Say you set it to 20/100 and paint. It just wipes out the old texture. Turns out 2/100 is really 20%, and 10/100 or more is just 100%. The same goes for brushing in standing grass.

Photoshop people tell me never hand over a psd unless it’s to someone you know will be using photoshop. Otherwise you’re just wasting megs. Won’t hurt the build, but will bloat your Project backups. jpeg seems fine for terrain.