Managing ASM policy after it's in blocking mode

The answer to your questions is "yes". The benefit of the the Real Time/Automated builder constantly running is that it will Track the Site changes(provided this setting is on), so when your application changes the policy will learn the changes (makes sure you configure your Trusted IPs for that!). If your application is not changing (e.g. it is something like Web Outlook) then there is no need to learn - there will be nothing new.

Once you understand ASM good enough you will be able to build your policies manually and switch off the RealTraffic builder. As an ASM consultant I always build all policies manually.