Considering the Wavefront obj file format where this syntax fits in the Chomsky hierarchy and why ? I'm also not sure if PEG grammars are being considered in the kind of classification made by Chomsky and if an obj is a real example of a PEG grammar .
to formalize this: what kind of grammar and parser I need in order to read an obj file ?
Depends on how you look at it.
The syntax (line per line first few chars show what the line is) is simple and a regular language.
The kicker is how to verify the f lines, however when you are parsing you have a turing machine at your disposal and you should just focus on the regular part and step in with the higher level where needed.
