What is the difference with different boot lids on different year beetles and the amount of vents in each. Do you have to have them on the boot lid???

The later deck lid shape started in '68 in Aust. and in '71 (I believe) put the wider fan with the offset (doghouse) oil cooler. The wider fan uses 20% more air so the extra vents were put into the decklid, 2 sets the first year and then 4 from then on.
If you have the wide fan/doghouse cooler combo, you need the extra vents no mater what year car.

Feel free to correct me on any details

Thanks so much for the help. Really appreciate it. Just don't like all the vents in the boot lid, wondering if I could of filled and shaved them out, but guess not.

We used to have a 1970 1300 'Standard' and it had no nents in the decklid

Your 70 1300 was still single port with the smaller fan which is why it had no vents.

As Matt said the bigger twin port doghouse fan started in 71 and VW never sold any twin port cars with non vented lids as the bigger fan needs more air than it can get with non vented lid

Yeah is the 1600 engine.