Hi Brendan
I’ ll be honest Brendan I struggle to get my head round music theory, for me if it sounds right I am happy.
I checked and @BanjoBen does have ONE lesson in D Tuning. It would be great if he had a few more but I know he has a long list of requests already and I’ve no wish to burden him with more.
https://banjobenclark.com/lessons/whiskey-before-breakfast-d-tuning-banjo-intermediate
It seems like many songs in G are just a step or two too high for me (and listeners) to sing. They say the average person only sings up to a C or maybe D note and many songs in G go higher. E tuning and capoing to F would help but how do guitars, mandos, and fiddles like playing in E or F? Or is it more practical just to stay in G tuning and play up the neck?
Sorry I can’t help you much with the singing. I know when I used to jam I would sing songs in the key of G, C, D, Bb and A at least that’s the keys the other group members played in I just sang lead the other guys filled the harmony. I should add I wasn’t very good.
A competent player can, but bluegrassers don’t prefer to center in those positions in general.