My husband and I (he's American and I'm Canadian) applied from Vietnam via Ha Noi. It was very fast and easy. I think it would be easier to apply and get it done faster in Vietnam.
Proof of current location = airbnb reservation + passport entry stamp for Vietnam.
It depends at what embassy you're applying. I am Canadian, I used all mutual fund locked in retirement investments and was approved. (Applied through Ha Noi in Vietnam.)
TFSA and investments should work. It may depend where you apply. I applied through the embassy in Hanoi as I am already over here. The statements I provided were all investments. Mutual funds, RRSP and TFSA held in Canada. Approved, no issue. I provided no statement that would be a liquid asset.