No, it's not possible to change the path of the local Lightroom Library file (but it IS possible to change the location for any locally stored originals).
Yes, you can delete the local library file without impacting your images in the cloud....provided that syncing is fully up to date. Understand that when you import images into the Lightroom desktop app those images are first copied to your hard drive using the location set in the Preferences>Local Storage tab. Then Lightroom syncs them from that locatioon to the cloud, which as we all know isn't quick. The default location for those imported files is inside the local Library file, so if you haven't changed that location and syncing of your files hasn't completed, deleting the local library would not be a good idea. Furthermore, after deleting the local library, it will automatically be recreated when you next open Lightroom, but minus any originals if they were stored in the default location.
Are your raw files in the cloud? Only you know that....if you still have syncing activity in progress, they might not be. If you have syncing paused, they might not be. If the app status (click on the Cloud icon) shows "Synced and Backed up" then they should all be there. You can double-check that by opening your LrWeb app (use any browser to open lightroom.adobe.com using your Adobe login details and you'll get a similar view to the desktop Lightroom app, except this is a view directly into your cloud catalog, not the local catalog). If the All Photos totals match, then yes all your files are in the cloud.
One more thing to understand...as I said, new imports are copied to your hard drive, from where they are synced to the cloud. However, those locally stored files are unlikely to be deleted immediately after they have been synced.....there's a complex set of rules which determines when the local copies are deleted, which might be days, weeks, or even months after they were imported. And if you have your preferences set to "Store a copy of all originals locally" then of course they'll never be deleted.
So before you do anything rash such as deleting the local library, best to check to figure out why it's filling up your hard drive. Suggest you post a screenshot of the Preferences>Local Storage tab and we'll help you figure out the best action to take.
Yes, all the imported files are temporarily stored on the hard drive. Yes, they should be deleted automatically, though that may take a long time, and depending on your settings they may never be deleted automatically.
They CAN be deleted manually, but you don't have to delete the entire Lightroom library file in order to do that. If you have them stored in a different location, you can delete that separate originals folder. But if you have them in the default location, which is inside the Lightroom Library package you can use Finder to show the package contents and then drill down the folder structure until you find the "Originals" sub-folder which you can then delete.
I don't know what "temp" contains, but that shouldn't be your raw files....as I said, they'll either be inside the Lightroom Library package or elsewhere in a location that you would have specified in the Preferences>Local Storage tab.
It would be a lot easier to post that screenshot I asked for, then I can be more specific about where your data is being stored.