開圖 is right. Both of them have several meanings used in different contexts.
Except for the usages he pointed out, I thought of another one.
"一个随意的人“ vs “一个随便的人”
In this case, they are both used as adjectives. However, they have totally different meaning and sense.
我是一个随意的人，saying I'm easy going.
他是一个随便的人，indicating probably he always has casual relationships with many women and never be serious to any of them, kind of negative.