One of my client has URL parameters on the main category pages on the website (e.g. www.example.com/category?utm_parameter)for some tracking. Will adding these parameters to GWT as Let Googlebot decide impact the performance organically for the main URLs? as there are no duplicate pages. Should these be blocked? 
How should UTM parameters be configured in Google Search Console URL parameters tool?
seo;google search console;google search;url parameters