I think this question, as is the case with most of poker depends on a lot of things.
Generally, PKOs shouldn’t be late registered because some of the prize pool will already be take out in the form of bounties awarded but I tend to register a minute or two after is starts because I feel covering everyone except the person/people who won the first pot or two is worth more than the small chance you’ll get dealt a all in cooler on the first hand.
With regular tournaments I think it depends where you think your edge comes from. If you have an edge on the field deep then you should register as early as possible. If you have a really strong 40bb game then you can hop in there any maybe look to play a few more tournaments a day.
I will tend to play a large amount of the registration period of the tournaments I’m planning on playing, but I will late reg some others, especially when I think I can make the money pretty easily with the pay structure.