Training for those would possibly hold you back from your REI strategy.

One of the best strategies is using other people's money, like private lenders or seller financing.

Seller financing seems like a great strategy if you can keep the bureaucrats happy.

I am an investor friendly agent with 8 properties myself and doing str, medium term, long term and rent by the room strategies.

VA Loans / House Hacking is typically an excellent strategy

You are making the right move by going to RE, IMO.I think you have the right idea on the strategy. 

What strategy are you looking to do?

i would say it depends on the overall investment strategy. im not really familiar with STR rentals in your area. personally i like the long term rentals, especially if you are trying to be hands off. we have two STR's, one we manage ourselves in FL and the other in Gatlingburg which is managed by a company. even with an STR rental company, i still find myself managing the manager. both require work and are by no means passive. long term (to me) is nice given time investment. hope this helps. 

Any tips on filling Vacancies, Arbnb experience, high or low rental season strategy?

Bumping the deductible up is probably the best strategy as you generally only want to file a claim for major damage.