Yes, as long as you have all programs closed, you can safely delete all files that have a .tmp file extension. They are temporary in nature only.

In my opinion, especially for those that are unfamiliar with which registry entries are safe to remove and which ones aren't, DON'T use a registry cleaner. Unfortunately, because they automatically remove lots of entries, it's tough to know which ones are OK to remove and which ones aren't.. Generally, I remove registry entries manually, one by one, when necessary.. Yes, I use registry cleaners occasionally but I don't recommend them for those who are uninitiated.

Next, as to all the computer optimization tools such a s Iobit, I just don't use them.. Just my opinion, but once again, I don't like the tools that do everything automatically. A program which recommends downloading and installing updated drivers when things are running just fine is something I don't like. If it ain't broke.... Something goes a little wrong with a tool like that and your computer has issues.. Windows already has a defrag program that will serve it's purpose when used occasionally. The same with Chkdsk. You can also fix other problems as they come up but in my opinion, those tools do very little to actually optimize performance.

Hope this helps.