Best log practice for log messages

We are starting with a new application and we want to use ELK stack for logging. We are not sure that we should use the plain text format or json format to log. We know that plain text format was previously very popular and while I am going through recent articles then json format discussions are going on.

Please recommend the best log format type like we should go with text or json format?

Well, one doesn't preclude the other. Plain text logs are easier for humans to read but JSON logs require less work on the Logstash side. If you have the option to use JSON, go for it.