tune to your voice
It took me years to realise I didn’t have to sing in the same key as the people I used to cover. Once I learned it was ok to adapt the guitar to my voice, not vice-versa, everything relaxed – especially my vocal cords.
Obviously you can just play in a different key to go lower. But when you’re picking in a non-standard tuning, that can change your guitar sound completely. If it does, consider tuning the guitar down instead. My Boucher sounds fine at D or even C# instead of E in standard tuning. Often, I take DADGAD down a semitone too.
Just to be clear: I normally leave the guitars tuned lower, then use a capo if I need to go higher. Particularly on stage, frequent twiddling is not a good idea. Especially when the G-string goes ‘ping’.
Slightly thicker strings are a must if you’re tuning down to stay. They help with intonation, and will usually prevent string buzz. I generally use Elixir 12-53s or thereabouts on the Boucher and Martin 11-50s on the Martin Backpacker. For many fingerpickers that’s probably too thin anyway; to each his own.
Speaking of intonation, I use SOS plastic spacers at the zero fret on all my guitars. I like to think they help, especially in weird tunings.