I do not agree with Brian,"English Folk Stuff"is only partly modal,at lets 50 per cent is in major key, and is suited to standard tuning, much depends on the competence and skill of the guitarist[ no reflection on any contributors on this thread.
Shetland tunes seem to suit standard tuning using jazzy chords listen to peerie willie. Irish tunes are more complicated harmonically, and imo work well in open tunings AND standard or drop d [have a listen to artie mcglyn].
dadgad is not as versatile as standard tuning, but has advantages as regards really different inversions[leaving out the third note that defines major or minor] for song accompaniment i like to use standard drop d and and a partial capo[which gives a similiar sound to dadgad], the advantage of the partial capo on gigs is that the performer does not have to keep retuning, and can switch between two tunings quickly.
I also use two tunings related to 5 string banjo dgdgbd AND DGDGCD