RAM won't help boot time.

Probably not. Boot time is almost entirely determined by your storage drive—HDD vs. SSD, and the quality of the SSD. RAM capacity helps once the system is running, not while it’s loading the OS into memory.

If you were running on 4GB and constantly swapping during boot, then going to 16GB might shave off a few seconds. But the limiting factor is still how fast your drive can read the operating system files. A slow HDD will bottleneck any amount of RAM.

On a modern system with an SSD, upgrading from 8GB to 16GB changes boot time by maybe a second or two. Not noticeable. If you want faster boots, get a faster SSD or enable fast startup in Windows. That’s where the gains are.

Focus on the drive, not the sticks.