The second diagram creates a circular relationship and I would recommend against that. It doesn't make sense that both the parent and the child tables would have a 1-m relationship with the same table. If the type is the same for all items on an order, then the FK belongs in the parent table. If it can be different for different detail rows, then there is no way there can ba only a single value in the parent record.
I would use two tables rather than three.
T1:
TypeID (autonumber PK)
Type (unique index to ensure no duplicates)
TSub:
SubID (autonumber, PK)
TypeID (FK to T1)
SubType
In Product, you would keep ONLY SubID. The RowSource query for the combo would be
Select SubID, Type & " - " & SubType As FullType
From TSub Inner Join T1 On TSub.TypeID = T1.TypeID
Order By Type & " - " & SubType