I'm wondering about subtle differences in
/r/ sounds across varieties of English.
By subtle I mean I want to ignore the obvious large differences such as the trilled "r" in Scottish English and the various rhotacised vowels in American and Canadian English.
I'm also not asking about tapped or flapped "t" or "d" sounds which could be characterized as kinds of "r" sounds.
I want to know about characteristic differences, if they exist, between the "r" sounds in English varieties at the phonetic and phonological level. I notice that different dictionaries which use IPA choose different symbols for the "r" phoneme, but this could be for reasons related more to typography than the actual sounds.
Are there differences which would influence the choice of IPA symbols or diacritics in either phonetic or phonemic transcription? Are there differences too minor to show in transcriptions but still analysable?