Rhythm is as deep of a subject as lead playing, but it took me a long time to realize that.That's a veritable encyclopedia entry about adept rhythm playing! Part of what I really like about Gypsy jazz is that the rhythm playing is so much about percussive patterns, but at the same time, there's plenty of room for incorporating all the approaches you mention. Personally, I really like to use something in between Freddie Green and triads on the middle strings -- four-note voicings where the guitar is moving that bass note around as well. (Except when it's not, and you're throwing in a half-diminished as a sub for something or otherwise abandoning the bass note.)
I'd never been purely a rhythm player, but when I got an invite to fill that role in a trio with a Western Swing steel guitarist and a lead player who could play circles around me, I jumped at the chance. I think it made me a better player, just from figuring out how the heck to carry the bass and provide colorful voicings at the same time. I love playing with people who are better than me and working to get up to their level. Unless they're jerks, of course.
Given your knowledge, I would love to hear some of your playing! I don't think I ever have.
As a rule, in most keys, the chord built on the fifth degree is a 7th, and is referred to as a Dominant. The Dominant is sort of a steering chord, because it almost always resolves to the chord built on the first degree of the scale, the Tonic, and if a Dominant doesn’t resolve to the one-chord, it’s very noticeable. In 12 Bar Blues, in Major keys, the I, the IV and the V are all 7th chords. Blues sort of has some different rules.Dominants? Are 7th chords dominants?