ᐅ Is it practical to build a prefabricated house using a solid construction floor plan?

Hello everyone,

We have just purchased a plot of land in NRW. The previous owners had already hired an architect to fully oversee the construction using traditional masonry methods and have already paid over €50,000 (about $54,000) for phases 1-6. There is already a building permit / planning permission, so construction could start almost immediately.
However, we are planning to build using prefabricated construction and are now wondering how to proceed best. The previous owners have offered to sell us their plans. Either way, we would still need to modify them (aside from the exterior dimensions) to fit our requirements.
The plot is on a slope, and there aren’t many options for building on it, so the design would likely be very similar either way.
Does it make sense to buy the plans from the previous owners and then work with the architect to incorporate changes before approaching prefab house manufacturers? Or are the floor plans not very useful due to the different construction method, making it more reasonable to hire a different architect for a new design?
And if you were to buy the plans—how much would you pay (they don’t really have a strong bargaining position)?

We are completely at the beginning of our home-building journey, so I apologize if this is a naïve question... We just don’t really know the best way to start.