Both concerns are legitimate:
1. Copyright protection: Under current USCO guidance, purely AI-generated images likely lack copyright protection. However, if you substantially modify the outputs (compositing, manual editing, selective curation as part of a larger creative work), those human contributions may be copyrightable. The more human creative input you can demonstrate, the better.
2. Platform terms: Midjourney's paid plans do grant commercial use rights. You're likely fine under their TOS. The risk is if their terms change — most platforms reserve the right to modify terms with notice, and your continued use = acceptance.
Practical protection strategies: (1) Add substantial human creative elements to each piece, (2) keep detailed records of your creative process, (3) build brand recognition (your brand IS copyrightable/trademarkable even if individual images aren't), (4) diversify across platforms so you're not dependent on one TOS.