Can we set up some purchase orders use position approval hierarchy and some transactions don't use

Hi,

we are using oracle version 12.2.5

we are setting position hierarchy for approval purchase order.

is it one time setup ?

can we set up for some transactions purchase order using position approval hierarchy and some transaction PO no need posisiton approval hierarchy ?

or we have to choose only one (using position hierarchy or not use position hierarchy ? cannot set up for partial so user can choose want to choose using approval hierarchy or no ?)

if we set owner can approve, is it using approval hierarchy or not ? )

Please advice

thanks