M1 Mac RAM and storage can be upgraded after purchase, but it's not easy - 9to5Mac
Amazon.com: Odyson - 512GB SSD Replacement for MacBook Air 11" A1465, 13" A1466 (Mid 2013, Early 2014) : Electronics
macbook-air-ssd-upgrade-harddrive-replacement - Tekkie Help
How to Upgrade MacBook Air Hard Drive (Original/2008/2009): EveryMac.com
Amazon.com: MCE Technologies 256GB SSD for MacBook Air 2015 and MacBook Air 2017: PCIe-Based 4 Lane (x4) NVMe SSD Flash Storage Upgrade - Requires macOS 10.13.x (High Sierra) or Later : Electronics