Effects that modify the creature's power and/or toughness, such as the effect of Overprotect, will apply to the creature no matter when they started to take effect
Aside from keyword "big" however, Fiend Artisan does have quite the activated ability too: "X B/G, tap, Sacrifice another creature: Search your library for a creature card with converted mana cost X or less, put it onto the battlefield, then shuffle your library
For example, if you put it on your 3/3, you can activate it only after it's unblocked
Ossification is hyper-efficient, Sheltered by Ghosts is great for aggressive decks, and Imprisoned in the Moon and Song of the Dryads turn bomb permanents into lands
Table of Contents show What Are Blue Creatures in MTG
You can't really set out to build an archetype like mono green control and expect to be winning the event with it but you can feel extra good about it if you do