If you make any scenes addressable, it’s best to make all of them addressable to reduce the chance and volume of unnecessary asset duplication.
For groups that will generate AssetBundles to be hosted remotely, be sure to enable the AssetBundle Cache. This setting will ensure that downloaded AssetBundles will be cached on your players’ devices, preventing them from having to redownload each session.
While it’s always good to keep in mind the runtime implications of many small bundles versus few large bundles, these considerations become more relevant when considering other goals you may have.
Efficiently delivering remote content to players
If your primary goal is the efficient delivery of remote content, your group structure should reflect how you aim to split content between “local” (i.e., assets included with your player build) and “remote” content (i.e., assets hosted on an external content delivery network). Again, be sure to enable the AssetBundle Cache to cache downloaded content on players’ devices.
The size, number, and Bundle Mode of these groups will depend on when you expect to deliver remote content to your players and how long you’re willing to let them wait for downloads to complete. For example, if your game’s structure will allow for delivery of all remote content shortly after they install the base game, you can opt for larger groups with Pack Together or Pack Together By Label, which will result in a small number of large downloads.
If you expect to deliver smaller sets of remote content to players throughout their sessions that will be less disruptive to the experience, you can opt for smaller groups and/or a Bundle Mode setting that will generate smaller AssetBundles that will download much more quickly.
In most cases, for groups containing remote content, consider Enabled, Excluding Cached for your AssetBundle Cyclic Redundancy Check (CRC) option. This will provide additional assurances of your remote content’s integrity as it’s being cached to players’ devices, while avoiding the additional overhead of performing a CRC for loading content that’s already on player devices.
Optimizing runtime memory usage and performance
If your primary goal is optimizing the game’s runtime performance and memory usage, remember the most important rule of Addressables groups organization: Assets that you plan to load and unload at the same time should be grouped together.
Generally speaking, this will mean creating smaller AssetBundles. You can achieve this in several ways, including creating smaller groups and/or avoiding the “Pack Together” Bundle Mode in your Group Settings for large groups that contain assets that won’t always be needed at the same time in your game.
You should also keep an eye on runtime performance to help you spot potential issues or areas of optimization. Take advantage of official Unity tools like the Unity Profiler, the Memory Profiler package, or the Addressables Event Viewer, which can all help optimize your game’s performance.
Be on the lookout for the upcoming Addressables Profiler Module, which will replace the Addressables Event Viewer. This new tool will provide even more in-depth information about how your code is loading and unloading addressable assets and AssetBundles, including detailed information about dependencies among your assets and AssetBundles.
Multiple goals
Of course, most projects will have a number of goals associated with Addressables. In this case, there is truly no one-size-fits-all approach. You will need to evaluate the tradeoffs outlined above and find the group structure and settings that will best achieve the success you’ve defined.
We recommend that you take advantage of the Addressables Build Report and the Addressables Profiler Module, available soon in Addressables 1.21.3. The Addressables Build Report will provide you with detailed information about the AssetBundles that were generated from your Addressables builds, including file size, potential duplicates, and in-depth dependency information. The Addressables Profiler Module is a new runtime analysis tool that takes advantage of this new dependency data, providing precise information about what was loaded by your Addressables code and why it was loaded.
Source: Unity Technologies Blog