While trying to answer an etymological question, I was looking through several different online resources about Etruscan vocabulary. Annoyingly, although these resources use mostly the same transcription system, there are a few significant differences.
Specifically, some sources use «th ph kh» for 𐌈 𐌘 𐌙, while others use Greek «θ φ χ» (sometimes substituting Latin «þ» and «x»). And some seem to mix the two styles: Wikipedia "Etruscan language" mentions both zilaχ and zilath as words for "praetor".
When a source uses both digraphs and Greek letters for the Etruscan aspirates, is there a reason for this? For instance, do inscriptions distinguish between 𐌈 «θ» and 𐌕𐌇 «th»? (If so, are there theories on what the distinction could mean phonologically?) Or is it just inconsistent editorial preference, like macrons on Latin vowels?