Secure Act adding SH NEC

Plan wants to add a SH NEC via the Secure Act provisions.  This gives them ADP SH but not ACP.  The plan typically only passes ACP using borrowing.  Can they still borrow from the ADP if it is SH?  Also, testing method was prior...I assume they should amend to current for the ACP portion?

No. Borrowing is only available to satisfy ACP if the 401(k) portion of the plan is subject to the ADP test. See 1.401(m)-2(a)(6)(ii)

No need to switch ACP to current year testing, unless they want to.

Follow up question:  The plan makes a discretionary match of 25% up to 4%.  If they use the new Secure Act SH NEC option, are they ACP Safe Harbor as well.

No. SECURE removed the notice requirement for the ADP safe harbor of 401(k)(12) and 401(k)(13) but did not remove it for the ACP safe harbor of 401(m)(11) and 401(m)(12).