Configure sp_add_schedule to run on the first day of every X months/weeks I need to configure my jobs scheduling dynamically.

The jobs will always run on the first day of the week once every X weeks. Same for months.

Looking at the documentation,

I see that for weeks option I would need to use freq_type=8 (weekly) with freq_interval=1 (Sunday). But which parameter should be used to mark that the repetition should be once every X weeks?
I believe @freq_recurrence_factor is the parameter you are looking for.