Yes, it means that these Immortal Foundations do indeed use one of the power systems as the core, then cover other power systems.
No, it means there are other choices; he can choose between fusion coverage and non-fusion coverage.
Non-fusion coverage needs no explanation, using one power system as the core, combining with and coexisting alongside other power systems.
Fusion coverage is using one power system as the core, then absorbing and refining other power systems, using them as nutrients to strengthen the primary core power system.
Of course, this choice is very flexible; you can choose one core, two cores, or even all systems if desired.
So....
Su Yu immediately transmitted his voice to the ancestral teacher, detailing the current issue he faced thoroughly.
Master Xuanwei spoke almost without thinking:
"Fusion. You have five core systems now, which is too many. You should select at most two, and refine the others as nutrients to strengthen the core."
