You can't have a curved surface. Thats all. Just be careful when moving vertices. If you get a curved surface (bad manipulation), there is another way to make that shape. It might take some creativity or some modeling in MED or something else. Unsure if A7 does anything about that issue or not.
A model shows as its bounding box in Gamestudio itself, but when you compile the map, it looks right.
The snap can be set, that changes the number of units an object can move when you move it. At two, it goes to quants at a time. At 32, it goes 32 quants at a time. Scale works the same way. Models can only scale in all three directs at once (don't know why, because they can be scaled by one axis in script). Blocks can be scaled any direction though. I usually don't use scale, just a personal preferance. I scale blocks by moving faces.