I entered pool in July 2016 so OINP has been closed ever since for me. I am planning to request police certificates and meanwhile if OINP opens and sends me an invite then I'll drop SINP, else go with SINP and withdraw EE.
No. SINP doesnt require ECA whether for OID or for EE sub category. Also, if you are following the paper based route, you will not need to submit ECA to CIC. Its not in the document checklist