I think it really depends on what your long term goals are. All 3 proposed methods (F2P+MTX/B2P+MTX/B2P) have positives and negatives. I personally believe that something along PoE’s model is the best for the long term success of the game, but is also founded on your ability to sustain the company until you reach a sustainable revenue from MTX.
Going purely B2P with no MTX means you end up with a model where your only income source is through paid content releases. You’ll get the most money upfront to establish your company on the back of this game, but you put yourself under constant pressure. You have to release content expansions with a price tag frequently enough to sustain yourselves, but infrequently enough or inexpensive enough that people are willing to continually pay to play new content. The major upside to that is not having to constantly outdo yourself on MTX releases. It lets you focus on THE CONTENT itself more heavily.
Going B2P with a ~small entry fee and MTX gives you a model where you get some initial cashflow, but will have a considerably smaller potential playerbase than F2P. This method will HEAVILY rely upon marketing. First, you have to get people interested in even looking at the game through content creators and marketing (which you’ve already started to do, I’m here because of pohx :D). Then, you have to convince players in your demo that the game is going to be worth that 15 dollar investment. You also can’t really have amazing armor or effects in game like you want because it will limit the long term potential of your MTX revenue.
F2P is, in my mind, clearly the best long term model. PoE is so successful because it drew in a small number of players that saw the vision of the developers and were willing to invest much more than a nominal 15 dollar entry fee to help them achieve that goal. Those players were massively more likely to get their friends hyped for the game, drawing in more and more potential MTX buyers. No entry fee means any random bored-person on steam can stumble upon your game and download it on a whim. Simply put, the more players that can stumble upon your game by chance, the more potential whales you have to fund you through supporter packs.
All that being said, F2P also puts you in a bind as a new indie developer. You’ll probably have to go massively in debt initially while the community forms itself and your whales emerge, barring an insane kickstarter campaign. B2P with no MTX tends to produce the highest quality games, but the least sustainable games. If you don’t think you’ll be able to form enough of a community to hit sustainable revenue before you go under, F2P isn’t really an option.