Which is the most efficient way to run a Monero full node on a bare-metal hypervisor?
The term "efficiency" can have a couple of meanings in this context. Efficient usage of resources, efficient time to install etc.
I was wondering what was the best solution (virtual server, LXC container or docker container on top of a VM)
In the context of efficient usage of system resources, LXC containers are light-weight, making use of the host OS. KVM by contrast is essentially running a whole separate OS. Therefore you could say LXC is more "efficient" than KVM. More answers here though.
What is the "best solution" is very much determined by your intended use-case and what else needs to run on the hardware. However, in the case of simply running a single Monero daemon, I can't immediately see the case for a full-on KVM solution.
and if there were already available pre-settled / trusted solutions
Trust is a sliding scale. I would say the most trusted setup is to build the daemon from source and install that on whatever system/setup you choose. Failing that, there is also the option of downloading pre-compiled releases from the official GitHub repository and lastly there is a Docker file, should prefer running Docker.