I use CrystalDiskInfo to monitor my drives. It shows the descriptive information about the drive(s) in my system, it has the temperature, percent life left for SSDs, and the raw SMART data.
WinDirStat is also a useful utility for figuring out what is taking up space on your drives.
Browsers cache to the SSD. I have absolutely no concern having the browser cache to the SSD
Majority of my data goes to a larger HDD, mainly because of storage constraints. I have a large Steam library. Most games or software are saved to the HDD. A few games are loaded to the SSD if there is an obvious benefit to saving the data there.
I have some custom GIS software that requires the data reside on the C drive. I have no problem letting it chew through data on the SSD if it means I cut 20 percent off of the processing time.