We are renting a campervan in Bergen the end of April.
Hope you are aware what you plan to do in terms of temperature and maybe last winter conditions - experience to drive snowy and / or icy roads. Most of the scenic pass (fjell) roads will still be closed at this time. In 2023 the Ryfylke road 520 was opened on May 16 and driving there looked like this photo. Streets closer to the coasts offer better chances to drive on.
Just to give you an orientation of seasons: apple blossom starts often mid of May (source)
Scenic route Hardanger incl. Flam is an obvious option. Be aware that sometimes the streets are narrow. For snow road Aurlandsfjellet behind Flam you would be too early - read part Vinterinformasjon.
Coastal streets to Stavanger and direction to Alesund are other options.
I would do such a tour earliest Mid of May, e. g. after joining Constitution Day celebrations on May 17 in Bergen.
In every case bookmark the live traffic map.