I don't know how it was before since I only recently started traveling more, both time-wise and financially, but now there really are good and reliable transfer companies. Start with the website https://atobtransfer.com/france/nice-airport-taxi/. AtoB offers really great and reasonably priced transfer services. It's not as cheap as the metro, bus, or train, but it's fast, convenient, and safe.

Are there any transfer services where I can book in advance? I know some taxis have this feature, but the price can change depending on demand when the driver picks me up. I need to plan my budget as accurately as possible.