Not all puzzles can be solved always
It is worth trying to open every chest you can find, but not each one of them can be unlocked right away.
There are also Norn Chests in Ragnarok, which you may remember from the first part. They contain items that increase Kratos' health and rage bars. However, in order to access them, it's necessary to solve an environmental puzzle. It consists in "extinguishing" the symbols visible on the chest. You have to find them first, and then appropriately respond to them. It may require hitting them in the right order and within a limited time, or setting fire to certain furnaces.
However, it is not always possible to do it. The symbols of some chests may located in places that are not available to you at the given moment. You may also lack the appropriate skills. It's worth trying to open each crate you come across, but it will not always be possible. The same applies to the other optional puzzles – you can solve some of them immediately, while others, you'll have to return to.
On the one hand, you could ignore them until the very end of the game before opening them, but on the other, it would be a shame not to take advantage of the hero development they offer. This is important, especially if you don't like playing on the lowest difficulty levels.