Learn Spanish (Spain): ¿Qué tenéis pensado hacer después del examen? - What are you all planning to do after the exam?

While both translate similarly, they have different focuses. The present perfect habéis pensado focuses on the action of thinking (Have you thought about...). The structure tener plus a past participle describes a current state resulting from a past action. Tener pensado followed by an infinitive is a very common fixed expression meaning to have in mind or to be planning to do something.

Would the word pensado change to pensadas if the people taking the exam are all female?

No, it remains exactly as it is. When the structure tener plus a participle is followed by an infinitive verb (like hacer), the participle is invariable and always stays in the masculine singular form (pensado). It only changes gender and number if it modifies a specific noun, like in the sentence Tengo pensadas las respuestas (I have the answers thought out).

Could I use the verb planear here since the English translation says planning?

You could say ¿Qué planeáis hacer?, but native speakers in Spain rarely use planear for casual, everyday plans. The verb planear sounds much more formal or calculated, like planning a complex project or a detailed trip. For casual intentions, tener pensado or simply the verb pensar sounds much more natural.

What is the slight difference in meaning between saying ¿Qué tenéis pensado hacer? and ¿Qué pensáis hacer?