If I use the custom Email option in the form's properties > Advanced tab > More Options, the header information (like IP address, browser, etc.) isn't displayed. Is there a way I can add it?

You can add header information using the code noted below for each field you want to include:

Date Submitted:
{BF_SUBMITTED:label}: {BF_SUBMITTED:value}

Record ID:
{BF_RECORD_ID:label}: {BF_RECORD_ID:value}

Form ID:
{BF_FORM_ID:label}: {BF_FORM_ID:value}

Form Name:
{BF_FORMNAME:label}: {BF_FORMNAME:value}

Form title:
{BF_TITLE:label} : {BF_TITLE:value}

IP Address:
{BF_IP:label}: {BF_IP:value}

Provider:
{BF_PROVIDER:label}: {BF_PROVIDER:value}

Browser:
{BF_BROWSER:label}: {BF_BROWSER:value}

Operating System:
{BF_OPSYS:label}: {BF_OPSYS:value}

User ID: (only works if user is logged in when form submitted)
{BF_SUBMITTERID:label}: {BF_SUBMITTERID:value}

Submitter Username: (only works if user is logged in when form submitted)
{BF_SUBMITTERUSERNAME:label}: {BF_SUBMITTERUSERNAME:value}

Submitter Full Name: (only works if user is logged in when form submitted)
{BF_SUBMITTERFULLNAME:label}: {BF_SUBMITTERFULLNAME:value}