AFAIK LE already has /var/log in memory. I could be wrong
tmpfs 879.3M 1.9M 877.4M 0% /var
The /var/ is a tmpfs, which means it's mounted in RAM, but in the case of logs, systemd's journal is used. In the /etc/systemd/journald.conf there's the following:
It's commented out, and the value points to what is currently used as default. So the default behavior of this mechanism is to store the log files under /run/log/journal/ , and the /run/ dir is also a tmpfs resource mounted in RAM.