If we use match instead of If, will it improve the performance

Well, I suppose we first need to define 'performance' here.

An a!match consisting of 5 components in my view is performing better than the equivalent, more compex, if-statement in terms of maintainability.

In terms of speed-performance, you can test both versions of some logic to see what performs better.

In my view nested if should not exist anymore going forward; use a!match for this.

I agree to what Laurens said. Performance in terms of Appian is always slow compared to any compiled language. An match is more maintainable than nested ifs.