[j_not_j]

For OpenBSD, only 512MB is needed even with the kernel relinks. Or so my experience with virtual machines says.

I sometimes run two VMs at 512MB each on my 4GB Windows 10 laptop. And I can use Windows apps too at the same time. (VMware workstation.)

If you want to shrink the kernel and the relink memory footprint, @unangst has an unofficial recipe.