RAM speed does not make up for capacity. If you need a lot of RAM for VMs or Docker or loads of tabs, getting lower capacity, but higher speed RAM is not a substitute.

For loads of tabs it does. For docker or VMs maybe not. Requiring a large amount of fully allocated RAM, like 8G+ seems like a deficiency in the software/dev environment, and definitely an edge case. In my whole career I've not needed that, but seen some poorly done dev environments configured with 4G+ VMs, so I don't doubt it can happen.