At TDC, the cam marks line up with the cam cover marks and if I recall correctly the reference mark in the crank is at or near the bottom. If you have the lower cover and crank pulley on, they would align with each other too. All of this should be covered in the videos, FSM and other materials you have. OTRAMM has some good stuff on Youtube.
If you don't have the old belt off yet, do it by the book - which is to say disassemble before, after or at TDC as the manual specifies. This location is usually specified so that the neither cam is in a position that it wants to rotate once the belt is removed.
Whether you assemble at TDC, just before or just after the critical thing to get right is the number of teeth on the timing belt between the reference locations on the crank, and both cams. Align belt to Crank first, then D/S cam, then P/S cam and take up the lack by the tensioner. If everything is 20 degrees advanced or retarded from TDC, that is just part of the normal rotation of the engine as long as it all stays in time with each other.
If you already have the belt off and are stressing out about this, I wouldn't sweat it too much. Whether you assemble it at TDC, just before, or after it is their positions relative to each other that is important. If it is disassembled and stable where it is, do it there. If something moves, move it back. Use your brain and a little care and you'll be fine. FWIW, I did my 05 at TDC.
LATE EDIT: Once you have the new belt on, check it by rotating the crank around twice by hand (clockwise) and stopping at TDC. Every 2 rotations of the crank , the crank and both cams should be at TDC at exactly the same time. You can tell this by matching the marks on the cams to the cam covers, and the crank pulley to the marks on the lower cover. The belt marks will no longer match and this is normal. The critical thing is that this all happens at the same time indicating these 3 components are in time with each other, which should happen the same regardless of where you assembled it.
If it is out of time, take it apart and re-time it.