I recommend identifying a strategy for your real estate investments first and make sure the market you choose supports this strategy.

In my case, I fall into the latter - I only invest locally therefore the Nashville market is the best for two reasons.1 - I sell real estate in Nashville and I have an incentive for you to choose this market.2- I know absolutely nothing about the other markets mentioned in your post. 

Regardless of where you choose to purchase your STR, there could be some upfront and potential time-consuming start up processes.

It's important to choose that one and commit to using it.

Just calculate based on how well you think the rental will do and choose the manager you think will best look after your property, even if they do charge a little more.

If a tenant isn't a good fit, I can choose not to renew their lease with a 28-day notice, as long as the lease is under 12 months and they've occupied the property for less than a year.

We all joined STR because of the cash flow, so why would anyone choose STR over LTR if it doesn't flow.

If the seller chooses to stay with me and sell, then I'll pay the agent a strong referral fee.It's a win-win-win for the referring agent, which gets me a lot of business.

I'll always choose the space that has a special feature or two like a fire pit, fire place, hot tub, nice deck for BBQ'ing, etc.

Choose that one and use it.