Everybody's choice is limited.

With a band - there has to be some sort of agreed running order - for the members to organise themselves, instruments. usually has to be something you can play very easily - so that if you hit sound problems - you can take them in your stride. Its also when you take in what the rooms capable of.

With solo gigs. The number has to either explain or reassure what you are about to the audience.

for anonymous characters like myself - the limitation is that you have to demonstrate your right to be there - technically. for acts whose personality is well known - there is a sort of paradigm for them to conform to - there are expectations that have to be fulfilled.