Yes -- it's safe to use all three...
1) is obvious
2) your harddrives 'spin down'-- they'll wake automatically -- unless you use the third option(s).
3a )In standby (I think) they will spin back up when you move your mouse/hit a key.
3b) system "Hibernates" (hibernation must be enabled first)-- it appears totally shut down, but it isn't. Windows saves everything the OS is doing at the power-down time you designate to an enormous file (called hiberfile.sys- I believe) saving everything that's active at that time. The advantage to this is that if you get distracted from your PC/ fall asleep

-- everything is saved... including all open running programs-- any 'unsaved' files in that Word document --whatever is running at that moment. It also boots a little faster-- because it's not really a "cold-boot". The disadvantage?? Hibernation sometimes has minor conflicts with 3rd-party stuff like Firewalls/Antivirus,etc. I don't know how well it would get a long with a UPS. And Hiberfile.sys gets enormous-- if you don't have lots of empty HD space-- it can cause issues that way.
3c) System shuts down normally... any unsaved data is lost/programs close-- just like you pushed the shut-down button.
PS-- If you use these-- I used to set my monitor for 45min/ HD 1 hour/ Hibernate or shutdown for 90 min. In Fla maybe you'd want it quicker on all 3-- and you have to be careful of what times your "automatic updates" of Antivirus scans are set to run-- mine are all at night... there are ways to have the apps "wake the computer" to do these things -- I haven't gotten that ambitious yet, though. (lol)