do you have to save the files every time when putting your poster into your mockups or can you delete them after uploading?

Is it okay to get Ai to put your posters in the mockups that the Ai has created themselves and skip the canva part or is it better to go through canva with the Ai mockups?

hi guys im starting out my etsy store and trying to align my store with something I enjoy so naturally would like to choose football based posters and was wondering if anyone knew of any copyright issues I could come up against when doing football stadium posters or football nationality kit posters or even specific football player shirts. Thankyou!