Addressing speed issues with new iMac

Having bought a new iMac (well, Apple Store Refurbished) and transferred everything from MacBook (worked very well), I was disappointed to see how slow it was going. Applications took what seemed like an eternity to open, thumbnails were slow to load, numerous swirling balls of death, etc.

After searching, I made a number of changes. I'm not 100% sure which of these (or which combination) did the trick, but it's now considerably snappier.

• Login items. For some reason, CrashPlan was listed twice. So I removed one instance. I also removed Android File Transfer, which doesn't need to be in place at login time.
• Based on this post, I ran the command 

rm ~/Library/Caches/CloudKit/CloudKitMetadata*;killall cloudd

• I contacted CrashPlan, as my backup seemed to be constantly in scan mode. They suggested:

1. Open the CrashPlan app
2. Double-click the CrashPlan logo in the upper-right
3. Copy and paste the following bolded text into the box: java mx 2048, restart
4. Press enter

CrashPlan will close to apply the change.

To confirm that the setting applied, reopen the CrashPlan application and repeat the steps above. This time type java mx in the command line window.