Try this

By passing form_view_ref: external id of form will load that particular form when you open with it. 
Also, to pass default values, send the value through context 
e.g. context="{'default_name': name}"

 <record model="ir.ui.view" id="crm_case_form_view_oppor_inherit">
            <field name="name">Opportunities</field>
            <field name="model">crm.lead</field>
            <field name="inherit_id" ref="crm.crm_case_form_view_oppor" />
            <field name="arch" type="xml">
                     <xpath expr="//field[@name='partner_id']" position="attributes">
                                <attribute name="context">{'default_name': partner_name, 'default_email': email_from, 'default_phone': phone,'form_view_ref': 'base.view_partner_simple_form','default_is_company': True} </attribute
                     </xpath>
             </field>
</record>