Conventional Loan - We settled at $155K and closed at the end of August with a 25% down payment and a 3.875% rate on our mortgage.

Once you have known costs, you can go back to the seller and explain that anyone that buys that home will end up doing the same that you will be required to do as their conventional or govie lenders will stop the loan based on the appraiser identifying these as unpermitted additions.

If it's 2-4 you can use a conventional lender.

I know that with conventional the downpayment is higher for multis maybe the lender got confused with conventional and FHA. 

We are looking for a conventional loan for a $1.2 million condo we put under contract in MN.

You may not be able to get a conventional loan until you've satisfied the 1 year requirement for the first one if you did it as an owner occupied loan.

I would like to take more funds for a downpayment on the single-family rental I inhabit - on owner carry or then FHA/Conventional if not.

Question, How would you do a conventional finance on a 4unit duplex that's technically a condo? 

If this is your first property and you are not house hacking then conventional lenders will typically require 20-30% down which in the case of the BRRRR is already built in.

I would expand the basement and maximize the property so that you can turn it into a cash flow positive asset and refinance it into a conventional loan and then re use the FHA.