Electrical – Overlap error (PCB design) using Eagle

There is a set standard package libraries called ref-packages-* look into ref-packages-smd-ipc.lbr. I usually try to search for a part by using package name: in schematics editor press "add" and enter *msop* (with "*" at begining and at the end) into search field.

I can recommend SparkFun and Adafruit libraries - these can be trusted and usually contain most common packages. This page has a set of decent libraries.

As regarding to devices it's usually faster to make your own than to look for them over the internet. If you download something you never know if you can trust them.

You are letting the DRC settings override the diameter. Use the "as defined in library" (or something like that, can't remember the exact name) setting. That's what it's for.