It is only about the repositories that the PDM itself can access to get its own updates. Using the update function for seeing available updates and trigger them from the PDM directly is working either way in my experience.
Small but important difference: the license of Proxmox products is primarily the AGPLv3.
What you are buying are subscriptions. In order to get updates from the enterprise repository (best tested, recommended for production) you need to have a...
You can't override how the Proxmox installer does it. You could install Debian and convert that to a Proxmox installation https://pve.proxmox.com/wiki/Install_Proxmox_VE_on_Debian_13_Trixie
If this is for a professional use-case, take a look at the Proxmox Offline Mirror which is Proxmox's official tool to make updates from the enterprise repository available to air-gapped systems and manage their subscription keys...
Sollte eigentlich nicht der Fall sein AFAIK. Eventuell, falls die VMs mit neueren machinetypes gestartet werden, kann sich vlt die virtuelle Hardware aus sicher des Gast OS ändern. Dann musst du, je nachdem was du hast, ein bisschen...
mach backups mit der integrierten backup funktion auf einen netzwerkshare. dann die clean install, und danach kannst du den share wieder als storage einbinden und die backups zurückspielen.
backups der gäste beinhalten die virtuellen disks und...
Disable any power saving features / c-states and/or switch the BIOS to a high-performance/virtualization pre-set.
10/40 Gbit can be a bottleneck if used with fast flash storage! Especially if it shares the physical network with other services...