The Point: Holy shit LXCs are so cool and felt like black magic getting "free" RAM back. If you're newer, like me, and have just been using VMs instead of LXCs, you should look at changing that.
I started my server back in November knowing absolutely nothing about using Linux, using CLI, or Docker. At the same time, I also went in raw, jumping straight into Proxmox on three nodes. As a result, I ended up using a lot of the Proxmox VE Helper Scripts for initial setup and have since gone back and learned how to do a lot of things myself. One of the hugely inefficient decisions I made at the time was to use a VM for Docker instead of an LXC.
For context, two of my nodes are running an i3-5005U and 8gb of soldered DDR3 RAM. One of those machines was exclusively running a VM to run Docker containers largely centered around downloads. On average, I was hitting ~30-50% CPU on the PVE host and ~7GB RAM usage.
Switching to an LXC has brought that down to 10-25% CPU and ~2-2.5GB RAM usage. A machine that felt like it was at its limit suddenly gained immense amounts of headroom.
Just wanted to put this out there for anyone procrastinating switching some VMs to LXCs. In my case, it was worth the relatively low amount of effort to free up such a significant amount of resources.