For a list of other such plugins, see the Pipeline Steps Reference page.
This value counts just the time spent on executing tests, and not including other time such as checking out the code, building the test, etc. For example, if your test job spends 50 minutes in tests and 60 minutes total from start to finish, then you have 10 minutes "fixed" overhead regardless of the number of tests it executes. If you use this mode and set the value to "10 minutes", then you'll have 5 parallel sub-tasks that all ends in roughly 20 minutes (20 mins = 10 mins tests time + 10 mins overhead.)
"N minutes per a sub-task" is a goal, not a hard constraint. So a sub-task can take longer (for example if you have a single test that takes more than N minutes.)
If disabled, the splitStep call will return a List<List<String>> containing the exclusion patterns for the different buckets.
If enabled, the splitStep call won't return a List<List<String>>.
Instead it will return a List of a structure with :