The “Direct Access 5 yr 6 mo Libor” may just be the lender’s name for the program. The most important document you want to review is the “Note” and all the riders. Those will tell you specifically if there are clauses that allow for additional access to principal. I find it unlikely that will be the case on a first mortgage.
If the mortgages are held by two different lenders “Chase”, “Franklin”. then you do need to make two payments unless your subject to contract is a wrap around or AITD, which would stipulate your payments go to the seller (bad idea) and he makes the payments (hopefully).