I agree. Stick to OG guide and GMAT Prep software for practice. There are plenty of problems. If you need more there are the OG verbal and OG quant books.
Using too many different sources can just confuse you further with what to expect.
Also don't be afraid to revisit GMAT Prep questions later. Most likely you won't remember them --and if you do remember them--you won't remember them well enough to get them all correct.
Worry less about where you stand and more on just trying to get as many questions correct as you possibly can. If you're getting them wrong, then revisit those questions a few days later.