Charlie
1. Regarding the first question, we need to find out the Auth Object that control's the access to the features in LTRC. Once we know which object has which access then we can easily control the Access to all the users for Stop Load/Replication. Personally I never tried as it was given to basis and we know what we need to do.
2. Regarding the Second Question for number of jobs defined in the initial configuration. Initial Load Jobs are dependent on the Data Transfer Jobs but not the calculation jobs. For eg: you can define 20 For Data Transfer and out of 20, you can define 15 for Initial Load. You can define Calculation for eg : 10 . But make sure you have enough BG available in the system when you define these jobs..
You can always plays with these jobs dynamically and don't have to stop the configuration to take affect. You can define more Calculation jobs when you parallelize the initial load and split calculation jobs and less Initial and Load jobs. Once the Calculations are completed, BG WP's are free and then you can increase Data Transfer/Initial load jobs.
Hope this answers your questions.
Mahesh Shetty