Hi Daniel, as a Miami-based Realtor who works with investors on new/pre-construction purchases, as far as location is concerned, I agree with your choices of Miami Beach and Downtown Miami. I would suggest you also consider North Beach (yes, it's a neighborhood within the City of Miami Beach, but deserves it's own consideration for several reasons) and Edgewater (blocks from Midtown). Here's why I like these neighborhoods:
North Beach - There's tremendous growth in this area. Starting with the Community Redevelopment Act (CRA) put forth by the city; the Monaco Yacht Club Residences which were completed in 2022 consist of 39 units that start at $3.25mm. There are 600 condo units and 100 apartment buildings in the works and/or will break ground soon. I'd be happy to share with you the CRA info.
Edgewater - North of Brickell and Downtown Miami is a large area with lots of newer high-rises and an incredible number of future tear-downs and developments. It also, currently only has one of the only STR options that has a true a live, work, and play mindset with a generous list of amenities, including restaurant. NOTE: This project will be completed prior to the 26/27 timeframe.
I hope this adds gives you some local insight into what's going on.