sending logs to SIEM

for both SPP and SPS if i configure the sending logs to SIEM is it only the Primary node of SPP and Central Management node of SPS that send it to SIEM or are all single nodes that can send it externally? 

Eventually is it possible to set only the primary node and central amnagmenent to send it?

Also: is it possible to export these events for SPP? from swagger with API's? what method?

for SPS is not possible to choose any specific event but SPS send all the system activities events, right? In which way i can know these events? (i have to specify to the customer that is asking me)

thank you very much!