Dynamics describes loudness of the notes.
Articulation covers all details and modification of the sounds of the note e.g. its timbre, length (e.g. legato vs. staccato), modification of note parameters like pitch and volume (vibrato, bending...), shape of attack, and others.
In some areas articulation and dynamics may overlap, e.g. accenting an note by playing it louder is form of articulation; starting a note quietly and then increasing its loudness (e.g. on a bowed instrument) could be perceived both as a certain articulation, and as a crescendo (dynamics).
In this view, various techniques of playing guitar, or effects applied to its sound probably mostly can be treated as various articulations, and in some cases they would also affect dynamics.
Now let's go through your examples:
finger-picked or picked, hammer-on/pull-off/tap, etc...
These are definitely various articulations. Typically hammer-ons/pull-offs are a bit quieter than normally plucked notes. In other words, hammer-ons forte may not be as loud as plucked notes forte.
Also does guitar dynamics include that "vowel sound" that is manipulated by direction/angle and force of pick? And also does it include the bright/mellow e.g. picking a string further towards neck as opposed to bridge to give a warmer sound, or vice-versa to give a more "tinny" sound?
This is articulation. In scores for guitar but also for bowed instruments the following articulation marks are used:
- sul tasto (or sul tastiera) for notes to be plucked/bowed near/over the neck
- sul ponticello for notes to be played close to the bridge.
Timbre changes can be also obtained by changing angle of the pick or finger/nail. On the other hand changing force of the pick would affect the loudness the most directly, so that would fall into the category of dynamics.
Does this term also encompass harmonics? Palm muting? muting?
Yes, these are techniques which produce different articulations. While for electric guitar the term palm mute or P.M. is typically used, in classical guitar scores we typically encounter term pizzicato (abr. pizz.), and also, more rarely étouffée for muting by pressing the strings on the frets, rather than next to them.
Various ways of muting strings to end the note are also articulations e.g. muting note sharply by touching strings with the whole palm in some distance from the bridge vs. softly, by touching gently with edge of palm (like in palm muting) at the bridge.
tone? Wah-wah effect (same thing as tone? I dno... )?
The topic of effects open Pandora's box, as there are many different effects, and even a single effect can produce very different sounds depending on how it is used.
I would say, that if an effect actively varies the timbre of notes throughout the piece, allows to accent notes (or oppositely, de-emphasize them) it's part of articulation. A typical use of wah-wah pedal would fall in this category.
On the other hand settings like guitar tone, or chorus effect statically present all the time are not articulations or dynamics, as they serve only to place the guitar sound in the context of the other instruments. However a chorus effect turned on just for the length of one note, or a phrase would definitely be an articulation, as it serves for emphasis.
Finally an effect like compressor/expander, even if permanently on, constantly decreases/enhances dynamics. Similarly auto-wah... I guess I need to stop here, but there is certainly way more to consider concerning effects.
