Guitar is divided into tonic and rhythm.
If there are only three people, it is usually three people, usually the lead singer and guitarist.
For example, greenday is like this.
I think the cello is ok, but I don't usually do it, probably because the sound of the cello is not as low as the bass. .
As for the classical guitar, it's nonsense to be a bass player. . .
Generally speaking, there are countless ways to form a band, from two people to countless people, but guitars and drums are generally indispensable, so drums are necessary. It doesn't have to be bass.
Cello can be used, but cello is not used to replace bass, cello is cello.
As for the performance of the art festival, it doesn't matter what form it is, just use any musical instrument, as long as you can play tricks.
I also formed a band in college myself. These are my own opinions. You can also change it again.
Thank you~