I have HCO AE i have the option to connect Saas Solarwinds observability. What are the limitation of using SaaS via HCO AE

You will need a SWO (SolarWinds Observability) licens in order to get access to your own SWO instance, from where you can start monitoring the things that you mention. Having a SWO license provides you the ability to do advanced cloud native monitoring but also allows you to tie it in to your HCO on-prem installation, to see what is happening "on the ground". It is currently not possible to see things that you monitor through SWO, in HCO. It currently works the other way around. The only things you can access on SWO from HCO, provided you have an HCO advanced license, are things like the AIOps service that facilitate ML for anomaly based alerting.