Most images are already set to auto-expand on first boot. If not:
Compress the resulting .img file with 7-Zip – it will shrink from 256GB to ~30GB. damaso 256gb raspberry pi 4 retropie backup image
: Because emulating later systems like Dreamcast can generate heat, a case with a fan or a large heatsink is highly recommended. How to Install and Set Up Most images are already set to auto-expand on first boot