I want to know the answer to the following question:
Characters with what marks can be displayed as a single character or a decomposed sequence?
All the background I'm provided with is that "For example, ḗ (precomposed e with macron and acute above) and ḗ (e followed by the combining macron above and combining acute above) should be rendered identically, both appearing as an e with a macron and acute accent, but in practice, their appearance may vary depending upon what rendering engine and fonts are being used to display the characters.". Is that enough to answer the question?
Answer: no