Yes, finishing reception and transferring to a mainline facility is a meaningful step up in terms of daily life and available privileges.
Reception centers like Kern are processing facilities. Their purpose is intake, evaluation, and classification, not long-term housing. The environment is restrictive by design because the facility is managing a constantly rotating population of newly arrived inmates who have not yet been assessed. Phone access, movement, programming, and privileges are all limited during that period.
Folsom is a mainline facility, which means your fiancé is now in a permanent housing assignment rather than a temporary processing environment. That shift comes with real differences. Phone access opens up considerably. Inmates on the mainline can typically make calls during designated hours rather than the severely restricted access that reception allows. Commissary, visits, programming, and recreation all become more accessible and consistent.
The specific privileges available depend on his security classification coming out of reception and his housing assignment at Folsom. Higher security levels within the facility come with more restrictions than lower ones, so where he lands within Folsom matters.
The first week or two after a transfer involves settling in, getting oriented to the new unit's rules and schedule, and getting his phone account set up with approved numbers. Once that is in place, communication should become much more regular. Make sure your number is on his approved call list and that there are funds on his phone account so he can reach you as soon as access is available.