What are the considerations while configuring a lead conversion process in Salesforce?

Hi Prachi,

When you convert qualified leads, Salesforce moves any campaign members to the new contacts. The leads become read-only records unless your administrator gives you permission to edit them. If existing accounts and contacts share the names specified on the leads, you can choose to update the existing accounts and contacts. Salesforce adds information from the lead into empty fields; Salesforce does not overwrite existing account and contact data.

For more detail please refer https://help.salesforce.com/articleView?id=leads_notes.htm&type=5