To take down a tank all by yourself, the best way is C4. It takes 3 C4 to be sure to kill a LAV, tank or boat. Jeeps and Armored transport (Humvees, Vans, etc) takes 2 for a sure kill.
Note that 2 piece of C4 might kill a tank if you put them on the right spot (mostly on it's rear from what I found). If you put two pieces on the sides, it will disable the vehicle and leave it burning giving time to the driver to jump out. If you put the 2 pieces of C4 on the front, it will disable but not put the vehicle on fire.
1 piece of C4 does a mobility hit for sure which can allow you to put more C4 instead of the tank running off.
Mines are also a good way to take care of tanks, but you must place them near it and hope it runs over it (or shoot them with the Rex/magnum/slugs from shotguns) or place them in popular spots for vehicles to get that random kill 5 minutes later.
For the launchers, this is what I found:
Also, I found this forum post:
For the damage stats versus vehicles per launchers, I could not find the stats. But I've heard that RPGs do the same damage as a tank shell. The angle is (like in BF3) primordial in BF4. If your rocket hits at 50 degrees, it will do around 20 to 25 damage while hitting a tank square on will do a disable in most cases. Tanks are also more resilient on the front to damage. Sides have less armor and even less armor to the rear.
Overall, killing a tank alone is easier with C4 since a good tank driver will rarely get killed by one engineer. However, to maximise your rockets potential, doing a 90 degree hit on the rear of the tank is the most effective way to kill it and the RPG is the one doing the most damage according to what I read.
Also, repair tools work wonders if you can sneak up on the tank, but that usually ends up in a suicide when the tank blows up (in BF3 you could survive with less than 10 HP, but in BF4 even if I stay at maximum Repair tool range, I still die).
Sources not linked before:
EDIT: Added mines,also, a guy took the time for 3 of the launchers:
EDIT: RPG vs SMAW analysis