Special Summon them, but their effects are negated, then, immediately after this effect resolves, Synchro Summon 1 "Mathmech" Synchro Monster using only those monsters, and shuffle the materials into the Deck instead of sending them to the GY
In slots, players have an eye on the RTP (Return to Player) percentage before making a decision
Beyond that, Niv-Mizzet, Parun is just the best Niv around, no doubt about it
The best deck is Tomato Control, a control deck that utilizes Mystic Tomato to hold board presence and allow you to easily access Witch of the Black Forest, and then Jinzo after that
However, the best general tutors are very expensive: cards like Vampiric Tutor, Demonic Tutor, Finale of Devastation, all these are in the double digits