We monitor about 500 windows servers and pull in the logs (OS, IIS) remotely today without have to install and agent on the server. Does splunk off option to pull in logs from a remote collection server?
Yes, this is possible.
You could install the Splunk Universal Forwarder on the remote collection server, which would allow the data to be encrypted and compressed when sent from the remote collection server to your Splunk instance.
Alternatively, you could do it without the agent, for example via a powershell script, but the solution would likely be less secure/scalable.