What time is the last bus from Yangshuo after the river cruise?

I am arriving at night and doing the river cruise the following morning.

Do I need to book in advance or are there always tickets on the day?

I know the tours brings you back to Guilin by bus but is there a later bus we can take if we want to do the trip solo?

My flight leaves the following day at 7am so not sure where is best to stay the night Guilin or YS?

Thank you for your ideas.
Helena