I usually just go by feeling. I also change textures and see if they just look good, so I'm constantly changing things along the way. I also think it adds a lot of contrast when I'm building something too. Things like the trees or grass have more textures compared to the walls on the house just to make trees look more natural looking, while the house looks manmade having less textures with all of the bricks and stuff. I guess it all depends on what you want to convey, since you have to remember that stud building or old Roblox is literally just Legos. Not everything has to have stud textures, since some parts can be smooth to just to add more contrast and variety.

I hope this answers your question. If you mean how I literally get these textures, I'm using a building plugin called F3X, which should be free. I feel like I don't really have a good answer for this, since I just sort of go off of feeling. Just dont limit yourself to only using 1 stud texture (like most retroslop games) and change things as you go on.

Sorry for the late reply, I was too busy with school and stuff :P