401K/403b Plan set up and deferral limits

A couple of questions:  If an employee has both Roth and pretax deferrals
1. Will the Roth 401(k) deferral amount and the pre tax 401(k) amount automatically shut off when the employee hits $17500?  I do not want to match any catch up. so do I need to build a separate catch up plan?
2.  In addition to the above, employees may also be in the 401(k) Plan and the 403(b) plan due to 401(k) deferral limits on the HCE's.  Is there way for the deferrals (401(k) and 403(b)) to shut off at the 17500 deferral limit.