Folsom, like Roseville, is really two different housing stocks. Old Folsom, the streets around Sutter Street and the historic district, dates back to the Gold Rush era with homes that have been through multiple plumbing generations already. The newer communities, Empire Ranch and Broadstone among them, were built from the 1990s through the 2010s and run standard copper or PEX from the start.
Folsom Lake and the American River corridor mean a lot of mature landscaping throughout the city, old and new sections alike, which keeps root intrusion a factor even in newer-construction sewer laterals if they're shallow or close to established trees. Tankless conversions are common across both eras of housing, for different reasons: aging tanks in the old core, undersized builder-grade units in the newer subdivisions.