The groups do cause higher CPU utilization in SWISv3. Dynamic groups are more taxing on SWIS and the database as they require more processing, but we are trying to optimize that as we find places to improve that in each release.
Also, if you haven't done so already...
In this file "...\SolarWinds\Orion\Solarwinds.Orion.Core.Dependencies.dll.config"
Please switch option ContainersEnableCache to true
<add key="ContainersEnableCache" value="True"/>
- You need to do that on each engine.
Restart the Collector DataProcessor service after this is changed (no need to do this if the option is already true.)
I believe that the above change I recommended for the containers thread count (MaxThreadPoolWorkerThreads) would help your performance even now.