The following key points will give you more information about application settings:

• If you want to specify a 64-bit environment for the web app, you need to make sure that the plan is in the basic tier at the least, because it does not support the free or shared hosting plans.
• If you want to improve the performance of stateless applications, ensure that the ARR affinity setting is disabled, because stateless applications don't save the client data generated in a session to be used in the next one, and that might lead to some instances serving more requests than other servers. However, if it is disabled, the load balancer will be able to distribute the traffic evenly.
• If you have Traffic Manager in place to load balance the traffic, it is recommended to disable ARR affinity, because Traffic Manager does not support sticky sessions.
• The key/value pairs you will be providing as application settings will be encrypted when stored.
• The connection strings are encrypted when stored.