In order for this to work the endpoint you're sending it to would need to be a service that is monitored by a OneAgent and that also supports the auto injection of the RUM tags. If your service already supported this you probably wouldn't need to be using agentless. So either way you're probably looking at setting up something new.
In that case the cluster activegate is 'cheaper' since you don't need licenses for that, but the upside to spinning up an instrumented webserver for this would be that server-side correlation can happen assuming other requirements are also met.
