Any of these options are more than powerful enough to compete at an FNM or even the Grand Prix level, so the build you choose is mostly about which style you like the most and how much you're willing to spend
This doesn't hurt your mana too much since it can give you the mana you need for spells, which you're going to have a ton of -- and it can permanently become a creature in the late game
Being cheap and easy to Tutor for are both nice boons, and the life isnt irrelevant
Giant Shark sports a lot of text that you dont even need to bother to read because it has all been updated in the Oracle text, which you can find on Gatherer, Scryfall, and some online collection trackers
Quite often youll see fast mana strategies lean on Paradox Engine as a win condition, because after dropping a few rocks they can usually cast as many spells as they can draw
This can be anything from an Ashnods Altar to a Deadly Dispute just pack enough ways to convert and youre laughing