My understanding is that you won't be DQ'd if you make lots of little errors which could be mistakes from missing one sign, etc and that others also made - even if it adds up to quite a lot.
You would get DQ'd if you are seen to have deliberately cheated, so drafting is a no - even if the advantage is not great - drafting for an hour saves you a few minutes - there is no way you can do it by accident. Also if you are judged to have ridden as a pair (stopping at the same places, riding together on successive days), that is not a mistake, it is deliberate, so DQ.
In the past I've thought that the penalties weren't enough to offset the advantage that people gained from them, so maybe they have upped them a bit this year.
But maybe not - @Samuli got half an hour total from a bit of A1 plus the bridge that I also did. That bridge saved me heaps of time as it opened up a much faster route so I would think a few hours would have been fair for that. And taking the gravel on the A1 was a pain, broke up rhythm, etc, so definitely worth more than a few minutes penalty.