But as for the seller finance, would the loan to the seller be the difference between 450k and the refinance number of 220k?

Advice will be different on each path.2.

Or for the high-end primary homeowner has no legal way to 1031 exchange; so the deferred sales trust is a no brainer.

Unless anyone else had a different experience? 

I am going to come at this in a different light.

Does this structure make sense for investors, or would you recommend different terms to make it more appealing?

Use a wide-angle lens so you can fit more of a room into the image, and try different angles to show more of the room. 

Outside of my primary, they are all cash flow positive, some to the tune of 3-4k a month on a 12 month outlook.

All depends on the interest rate on the primary home and if fixed.

Although whichever option you go with make sure you're also thinking about the long-term property value and what makes the most sense vs trying different angles now that negatively impact future resale/property values down the line.