So, I'd prefer for them to stick with me as I do want to invest in another rental every 2 months or so with the same structure listed above. 

I would stick to vacation areas that thrive off of tourism and welcome STRs year round.

One container house and one stick built.

Ideally, the person you choose should be someone you stick with long-term to make things easier.

If you want to do BRRRRs, it's probably better to stick to B or better neighborhoods, as they appraise better and have a higher likelihood of getting your equity out!

Most will likely stick to the technical limit of Sept 2021 when it ceased being a primary residence, but some may be comfortable going by the address on the 2021 return and others may explore a partial exclusion, depending on the reasons for your move abroad.If you'd like to read up on the technical rules, the IRS publication 523 gets into more detail than most people would like to know, but it does have some helpful tables and examples for different scenarios.

They really do stand out in a neighborhood plus I doubt you could get permits to build in a established area.Much easy to build on a larger plot of land in the boonies, which is where I see most of these.In the end, once you get them looking nice, you could have done a stick built house or even a log cabin if you can harvest materials on your land for about the same or less.

I have pretty good umbrella coverage so I think I'm sticking with one LLC for the 3 properties to at least separate my personal risk from the rental risk and covering it with a very good liability policy.  

Do you take all your cashflow and stick it into your reserves?

If there's something in the book you really want to learn, you will need to practice it over and over again until it sticks.