Importance of varchar length in MySQL table

VARCHAR is ideal for the situation you describe, because it stands for "variable character" - the limit, based on your example, would be 200 characters but anything less is accepted and won't fill the allotted size of the column.

VARCHAR also take less space - the values are stored as a one-byte or two-byte length prefix plus data. The length prefix indicates the number of bytes in the value. A column uses one length byte if values require no more than 255 bytes, two length bytes if values may require more than 255 bytes.

For more information comparing the MySQL CHAR to VARCHAR datatypes, see this link.

No, in the sense that if the values you're storing in that column are always (say) less than 50 characters, declaring the column as varchar(50) or varchar(200) has the same performance.

There's one possible performance impact: in MySQL, temporary tables and MEMORY tables store a VARCHAR column as a fixed-length column, padded out to its maximum length. If you design VARCHAR columns much larger than the greatest size you need, you will consume more memory than you have to. This affects cache efficiency, sorting speed, etc.