Move "touchless" POs through different approval workflow than standard POs

Hello all,

We currently utilize Standard PO document type for all POs.  However, we are currently implementing Position Hierarchy and PO approval workflow.  We have touchless POs that are created through min-max that we don't want to face Position Hierarchy and the PO approval workflow.  We want these to be approved without $ limit.

Should we be looking at setting the document type of these touchless POs to something other than Purchase Order Standard?  If so, where does document type get set at?  Is there another best practice that we should be using to separate out the POs we want to go through the PO approval workflow (with position hierarchy) and the ones that we don't?