There could be a delicate dance somewhat similar to what Soviet lunar lander was planned to do at launch: start all engines, and if all is well, shut down those backups. Here with Raptors one could imagine launching two engines, but if one runs well - during the startup sequence - shut the other down mid-sequence.
But this is totally question to Raptor creators. Might be not really feasible or even meaningful.
But this is totally question to Raptor creators. Might be not really feasible or even meaningful.