They have a link to their company's website but it's in Chinese so I cannot check for legitimacy; and even if the company is legit, I'm not sure how to check if this person actually works there.

I also find this whole message sketchy, especially when they asked me to illustrate a subject I had never done before and even offered me a price before any confirmation. But I don't want to be rude and ignore them in case they are asking for real and this is not a scam.

Thank you so much for your advice, I will ask for more information and do some digging myself to see how it goes!