Hi @Andy25341946tmf8
I'd like to inform you that Adobe Express premium users have the ability to resize the project anytime to meet their needs. The project can be scaled using social media presets or any custom size.
The size range of the post could be anywhere between [0.17-20] inches.
You may find Resize option on the right side of the Adobe Express Web app. (please refer to the screenshots)


Let us know if this helps.
Regards,
Amitej