Many lenders offer DSCR products on 30 year fixed terms.  

For DSCR, a 3 yr prepayment penalty and paying 1-1.5 points will put you pari passu with Conventional products right now for the most part. 

Slow and steady.

Finding STR viable properties and incorporating MTR strategy in slow months is what works best.Crystal Beach is an option as well as Palm Harbor - however a word of caution a lot of Palm Harbor is HOA and I would avoid that as well. 

Does anyone have any experience on working with them and/or their product?

This loan product has a VA inspection during your appraisal (nothing scary).

Incentivize production of rental unit's NOT just concentrated rental colonies (apartments) but across the spectrum. 

That’s a challenging situation since you haven't defined the final product yet.

Seller concessions go towards closing costs.Two options, in a slow buyer's market, seller takes it out of their list price.In a seller's market, it's more like what @Steve Vaughan said.

Yes, this is pretty normal - generally conventional loans like this are super competitive (since everyones essentially offering the same product) so shopping and finding some deals especially with smaller banks and brokers can yield good rates well under the "prevailing headline market rates"