Not really unless you are concerned about moisture. then you may want to get the electrical moisture tape to prevent corosion. other than that just clip it all up and plug n play..
No, you shouldn't. Just tape the sides only, the full length (so the tubs don't rip the flexwatt). It's easier to make all your connections before taping it down. Post some picts. of the rack when your done!
You also want to tape the opposite side of the flex watt from the connectors in a folded over piece of electrical tape. A small bit of exposed copper is present at the cuts and if you use the foil tape it can cause a short at this point or become live with electricity. Can be very shocking if you know what I mean!