FASTFR : This option is used to activate "The faster modal solution method" for modal frequency response analysis !
FFRS : The second means FAST Frequency Response Solver, used if you want to activate the external FASTFRS solver. This solver works well for a large modal frequency response. (You have to install it in advance).
FFRSNCPU : used with FFRS. It's useful if you want to define the number of CPUs to be used by the external solver "FAST Frequency Response Solver".
FFRSLFREQ : It's a threshold (cut-off frequency) used to partition your system into low freq and high freq.