Start by looking at parts diagrams for the valve train, to identify related elements. That will show if (for example) there is an hydraulic tensioner or filter screen before one.
Then you can look up the elements using part numbers and Google Images or Fleabay, to get a clearer idea of how they are in real life. The frequency with which a valve train element is offered for sale (like the BMW N46 models for which you can almost buy timing chains at the corner shop) often is a clue about component longevity or reliability.
For example:
https://www.ilcats.ru/peugeot/?funct...4A&language=en
Then you look up part 084922…
https://www.google.com.au/search?q=peugeot+084922
(I didn’t include the Google Images link as it was chockers with identifiers.)
In this instance, there doesn’t appear a huge market for link chains and guides, tensioners; this leads you towards the notion they’re fairly durable.
There is a sprung ball check valve, Peugeot number 023527, between the block and head (these normally are pressed into the head). It’s found on the pages detailing head gaskets etc.