Taking over a power of attorney for a friend – remuneration & tax? (Austria)

Hello everyone, an acquaintance (not a relative) asked me to take over the power of attorney for her in the event that she is no longer able to make decisions later. We have a notary appointment soon. She has around €108,000 in savings and a net pension of around €2,600/month. I'm wondering two things in particular: Remuneration: Does it make more sense to agree on an annual flat rate in accordance with Section 276 of the Austrian Civil Code (ABGB) (5% of net income + 2% of assets over €15,000), or rather a stipend