Can only special summon a monster when he is normal summoned.
Can only special summon level-3 monsters.
You can use Trident Warrior’s effect to special summon a Tuner from the hand and use them to Synchro summon into a powerful monster. Without the help of other cards, this combo can be used to Synchro summon a level-7 monster like Power Tool Dragon, Ancient Fairy Dragon, and Black Rose Dragon.
Similarly you can special summon Mystic Macrocarpa and reduce its level by 1 to Synchro summon a level-6 monster. Keep in mind that Mystic Macrocarpa Seed can only be used to summon EARTH Synchro monsters.