Can you install those components on the same machine and should you install those components on the same machine are two different questions which I will cover below.
First of all, for both Geoevent Server and Image Server, ArcGIS Server is required to be installed on the same machine. You can't have Geoevent/Image Server without ArcGIS Server installed on the same machine.
However, it is typically recommended the ArcGIS Server machines with Geoevent/Image Server be on their own dedicated VMs. Meaning you should have one (or multiple) VMs with ArcGIS Server installed that will host your feature services. Then, you will have dedicated VMs that host your Geoevent/Image Server sites (with ArcGIS Server installed on them, but not joined to your standalone ArcGIS Server site).
Now, yes, you can install everything on the same VM, but that's not going to be recommended because it will require a lot of server resources and you're going to have ArcGIS Server, Geoevent Server, and Image server all competing for the same resources. It's best to have separate VMs for each component.
Regarding your Monitor question, you can install Monitor on your Portal machine, but it's not necessarily recommended for the same reasons I stated above. Monitor will compete for the same server resources as Portal. It's best they be installed on separate machines.
Here is a good help document regarding best practices for Geovent system architecture. Best practices for system architecture—ArcGIS GeoEvent Server Help | Documentation for ArcGIS Enterp...
Another good help document about server roles, including Geoevent Server. ArcGIS Enterprise server roles—ArcGIS Enterprise | Documentation for ArcGIS Enterprise
