Load Balancing of Jenkins Nodes without Load Balancing Plugin?
This is similar to:
https://stackoverflow.com/questions/55023570/how-to-run-a-job-on-first-available-node/55567958

Have you considered Least Load plugin?

https://plugins.jenkins.io/leastload

By default Jenkins tries to allocate a jobs to the last node is was executed on. This can result in nodes being left idle while other nodes are overloaded. This plugin overrides the default behavior and assigns jobs to nodes with the least load.

Don't imagine there's a security issue there.