You are defining the group not the work centre on the line and therefore it is different. You could define the work centre but then you will have a capacity issue with step 2 because it would only look at the work centre defined. The group is to group similar resources, if yours can handle different process quantities in the same group you will have an issue unless you define the work centre on the line, but then you will have capacity issues. Have you tried looking at defining each machine by capacity rather than a time based setup?
Standard will look at the times set on the operation.
Capacity will look at the capacity of the work centre, so you do not define times, it knows the work centre can do 200 an hour, you are making 400 so it needs 2 hours.
The batch and work centre batch I guess look at the batch defined on the work centre or work centre group. The differnece and the processing I am not sure, they are new to AX2009 and are ignored in all help and manuals, so you would need to test and investigate.