I would say 885 sc's are the best resource after OG sc's. It's best to use them after doing OG sc questions so that you can apply your knowledge and new rules/idioms learnt.
The standard is comparable to ETS stuff as they are originally from old ets tests.
I remember when I first started doing them, I was doing 2-4 questions incorrect from a set of 10 questions. Eventually I reached a level where I was doing 0-1 question incorrect. It's very important to reflect over each question you got incorrect and also over those questions which though you might have done correct, you were still unsure of while attempting. Dont move ahead without understanding your errors otherwise the whole purpose is lost and you stay where you were.
Good luck.