Multiple installing is NOT supported.
There are not such official docs mentioned about that. And probably it will have conflict with environment variables, shared memory and few other things...
We support is configuring multiple web agent instance on the same box one each for different webserver instance (by specifying unique ServerPath)
This is documented here : https://docops.ca.com/ca-single-sign-on/12-52-sp1/en/configuring/web-agent-configuration/manage-web-agents-with-multiple-web-server-instances