After brief experimentation, it seems that plugins are scoped to the level of the vault, meaning that the installation and configuration set of plugins is stored in a vault, and not in some application configuration global to all vaults.
However, I have not found such an observation, which is significant because it represents a design quite different from in most applications, explained in any documentation or discussion.
Would someone please explain to me, who is entirely new to Obsidian, how installation and configuration of plugins is handled for the general use case involving multiple devices and multiple vaults?
Assuming my observation is accurate, is it the same for all application configuration, or rather, does the application maintain a global configuration?
Plugins are scoped at the combination of device and vault. More precisely, they are scoped to the config folder (.obsidian by default) of the vault. This can be synced between devices or not at your discretion.
Can the synching of the plugin scope for a vault be toggled on/off or is it a one time decision? For example, one might want to turn it on initially on a device newly added to the sync list to copy the plugin collection initially, and then toggle it off, allowing customization for that device.