And when using the Trident, if a batch is going to be processed on one bolt, can the batch run on different workers?
You can (but it is tricky). And no.
For 1) There is no configuration parameter for this. You can only configure the number of workers of a whole topology. However, you can implement a custom scheduler to assign the executors of a bolt to a specific number of workers.
For 2) A batch is a "unit of work" an cannot be divided. Thus, it can not be partitioned to multiple workers.