Rule Based setting

To match your competitor's price, you can set your rule to < Competitor's Price - 0.00 >. OR <

Buy Box Price- 0.00 >

However, there is no way to ensure you will match your competitor's price when you're in the Buy Box.

Matching your competitor's price is not advisable because you are not overtaking the position, so you might still be outranked depending on other factors, such as seller metrics.