You should check the behavior again. Actual hour updates will not change baseline data, but it will change work (or planned) data. You are also working with some difficult practices that are normally not best practice. Neither using 150 resources on a task or fixed duration tasks is best practice.
You can use timesheets, but updating the project whether from the task sheet or timesheet will update actual hours in the project plan and adjust work to match. Publishing from the project plan doesn’t affect work. It’s updating actuals from PWA back to the project that will affect the plan.
Hope that helps. I am trying to help with limited knowledge of the total picture so I apologize if it isn’t exactly what you are looking for.
