Holding down the Command key during launch overrides the Auto-start behaviour, regardless of the settings or which way you launch the VM. So you can always reach the config screens after a reboot.
However, I find it irritating to have to shut down and restart the VM in order to open up a narrow window of opportunity to edit ... or even to look at ... the settings options. This sort of highly modal behaviour is generally deprecated in Mac OS apps.
The most user-friendly apps I have used with this kind of issue allow you to edit the config at any time, but have some settings that will only take effect next time the app or document using them is launched. In this case those settings would have to be annotated to say that you must reboot the guest OS in order to use your changed settings, but I would recommend that Parallels consider providing this sort of behaviour.
However, I find it irritating to have to shut down and restart the VM in order to open up a narrow window of opportunity to edit ... or even to look at ... the settings options. This sort of highly modal behaviour is generally deprecated in Mac OS apps.
The most user-friendly apps I have used with this kind of issue allow you to edit the config at any time, but have some settings that will only take effect next time the app or document using them is launched. In this case those settings would have to be annotated to say that you must reboot the guest OS in order to use your changed settings, but I would recommend that Parallels consider providing this sort of behaviour.