M1 Mac RAM and storage can be upgraded after purchase, but it's not easy - 9to5Mac
Apple MacBook Air 11.6-Inch Core i5 1.6GHz 4GB RAM 128GB SSD Storage E
OWC 16GB (2x8GB) ram Upgrade PC3-12800 DDR3L 1600MHz sodimm 204 Pin CL11 Memory Upgrade Kit Compatible with Late iMac, Mac Mini, and MacBook Pro Computer at Amazon.com