16GB is the floor for AOSP builds.

No — build time won’t be cut in half moving from 8GB to 16GB, but 8GB is so painful that the comparison is almost meaningless.

With an 8-core CPU, a clean AOSP build is massively parallel. Each parallel job can eat 1–2 GB of RAM. On 8GB, the OS starts swapping almost immediately, turning your build into a disk-bound crawl. You might finish a full build in hours if you’re lucky