Hi Alina!
I think this will be hugely dependent on context, however here are some ways we use these two in South Africa:
1. Her books were spread out over the table.
2. He spread the map out on the table.
* spread out - to open or place something over a large area.
3. The group spread out as they moved toward the house.
* spread out - the individual people physically spaced themselves out over an area.
4. She stretched out her arms as she woke up.
5. The dog stretched out on the bed.
* Stretch out - the act of stretching (think of an elastic band being pulled on both ends)
6. She stretched out their supply of sugar.
* stretched out: she limited their use of sugar so that it lasted longer.
As I mentioned, context is important as this can change the meaning - these are just a few examples.
I hope this helped!