1
Define what must stay
If you have a source image, list the elements that cannot change: perhaps a person's identity, readable lettering or a product's shape. If nothing must stay, a generator may be the more direct starting point.
2
Test one representative task
Use a picture or brief similar to your real project. Inspect the full composition and difficult areas such as hands, edges and text. A result that looks convincing as a thumbnail may fail when used at its intended size.
3
Check usable access
Before committing, verify the selected service's current requirements and export conditions on that service itself. A trial result is useful only if you can obtain an output that fits the job.