What is the difference between 'if the data is of good quality' and 'if the data is tidy'?
Let me try to explain by intuitively. First let me take the easy one. 



Data being tidy

As per definition Tidy means Arranged in Order, Neat, Uncluttered. 
All of these explain the physical aspects of the data representation. For example, data arranged in proper columns, with good headings, with relevance etc. You can think of this being syntactic in nature



Good Quality Data

This refers to actual data elements in the file. Like not having too many blank (missing) values. Every column having proper data types. Data without special (unreadable) characters. Properly encoded. Not having too much unstructured data. You can think this as the semantics of the data.

Hope this helps