The slower the better?

is this true for dvd/cd burning, meaning is it true that if u write a disk at the lowest speed, it smore reliable using it to other drives and also is it longer lasting?

It’s a myth.

For DVD media starting off at the rated speed of the media , except maybe 16x media which may well burn better at 12x, is the general consensus here.

For CDs then for Audio stick to 16x & 24x for data.