If you are planning to live in it, I would go with an FHA unless you have a clear exit strategy, Typically when you use private funds or OPM, they will be shorter term loans. If you know you will be able to refi out of it and into a more traditional loan product, than OPM could make sense (that's where BRRRR can work if your numbers work to do this). Don't forget, you'll need at least 6 months seasoning if you BRRRR into a more traditional product. Also to consider, you'll get more favorable rates with any gov't backed loans like an FHA. I know people that use similar products as the FHA and buy a new house every 18 months or so and that's how they've been trying to build their portfolio. With 3.5% down, you may not have any cashflow, but it gets you into the property for less and you can start to build equity. Some of these answers will depend on your long-term strategy and what your next move will be.
Best of luck and congrats on making the move to invest. You won't regret it.