Shall I stay in Onomichi or Okayama?

On August 8th I will visit Onomichi coming from Yamaguchi, I did Shimanami Kaido before so mainly is to do the Senkoji and Temple walk and walk around the shotengai and the shore, I've heard is pretty small.

The next day I have to reach MATSUYAMA as soon as possible to have enough time to visit it since I am going to stay only one day in Matsuyama in a hotel right next to Matsuyama main train station.

So if I take the first combination of trains from Onomichi I will reach 10 30 aprox there there's an option of picking an afternoo/evenin train from Onomichi and sleep in Okayama and pick the earliest combination from Okayama which would leave me in Matsuyama at 8:30 but I am not sure if I will have enough time to enjoy Onomichi that way, what do you think?

Option 3 : stay in Imabari? Google maps tells me there are bus options from Onomichi to Imabari via Fukuyama until around 8:30 pm. You can arrive in Matsuyama at 7:09 am the next morning.