If you are just lowering with a modest drop then all you will need to do is do the springs. If you are looking to add Shocks/Struts, etc then you will need to upgrade the mounts.
You should do springs and shocks/struts at the same time because it will reduce your labor cost since they can be done at the same time.
i was planning to use the FRPP V6 springs for a 1-1.5" drop. i don't want to slam it because it's my wife's daily driver. but from what i have read, these springs require new dampers and strut mounts to fit the 2011+ cars.
You can do a straight switch, no issues with another brand, I can't legally say the name. I don't know much about the FRPP's.... Springs to Spring swap will cause no issues as long as you are not "slamming it"
If you just want to lower the car by changing the springs, then yes you can do that with our Sport/Ultralite springs without doing anything else. However, we do recommend changing the dampers and strut mounts while you are already there.
The strut mounts are much more durable than the stock mounts and will allow the camber to be corrected after lowering. Also, dampers will help get the most out of your better handling springs. We also recommend an adjustable panhard bar to re-center the rear-end after lowering. Shoot me a PM and I can get a package quote for you.