No. Calyx isn't a fork of Graphene. "CalyxOS draws heavily from the LineageOS community and code." In my experience Calyx wasn't a good fit. Have had best luck with Graphene. Its reported to be more technical than Calyx OS but I don't find it to be a problem. The issues most experience is when they try to load no free software and or FOSS that utilizes some sort of Google dependant. https://calyxos.org/docs/about/