All the features (like right-sizing) are not available for Partner users.
NX Platform for all cloud.
Please note actual partner users won't have access to Rightsizing feature in NX. It's enabled only for Direct and Channel tenants. Partners get to see Rightsizing by switching to their respective channel tenants.
Below is the list of features available for the partner user
Exception to this rule is users having TAM user affiliation/role have access to everything.