Yes management, execution, and agent all run on the same machine (Windows 2012 R2 Standard).
We do see errors from time to time with one workflow, it downloads files from an SFTP that sometimes contain invalid characters and it causes "AML is Invalid" errors in the event log.
Most of our workflows are triggered by schedule conditions (we have 60 or so conditions and workflows), we do use several file watchers. Most tasks invoked by the workflows move files, invoke other applications or scripts, and a few query SQL datasources.