I think the biggest and #1 misconception China has about Korea is that they often think Koreans are much more arrogant and vain than they actually are. I think their impressions of Koreans = nationalistic netizens. But those are not the everyday Korean people, just like how nationalistic Chinese netizens do not represent the average Chinese.
Since 2013 I’ve been back to Korea each and every year, and I’ve never met any Korean that hated China or thought that Korea was better than China or thought that Confucius/chinese festivals/chinese history/etc was Korean, never. Yet this is a widespread belief amongst Chinese people both I met in person and online, I’m not exactly sure why.
Personally from my experience (both online and in person), I’ve found that Chinese people brag a lot more about their country than Koreans do. Many Koreans actually dislike their country a lot (young peoples call it ‘Hell Joseon’) and one of the main differences I’ve found between Korean and Chinese is that Koreans lack a lot of self-confidence (either in their English or appearance or abilities, etc) whereas Chinese are very confident in themselves. So I don’t know how Chinese could think that Koreans are arrogant unless their opinion comes from nationalistic Korean netizens only (2002 World Cup controversy etc I’ve never met a Korean who actually brought up this topic in person, only online).
I think #2 misconception is that USA controls South Korea and can order it to attack anyone they want but its not true:
After becoming a democracy in the 1990s, the South Korean government assumed peacetime command of its 655,000 active military personnel.
The South Korean military coordinates closely with the Combined Forces Command and the United Nations Command led by U.S. General Vincent Brooks, who is also commander of the 28,500-plus member U.S. military force in Korea.
In wartime, the U.S. commander would assume control of South Korean forces as well, but it is not an automatic transfer of command. The South Korean president has to first agree to cede that control.
South Korea actually has full control over its military even in war-time in the near future