Yes but that's generally where folks start. The big shift for me came when trying to learn Stevie Wonder tunes. I could tell the supplied guitar chords weren't accurate and out of desperation I began painstakingly counting "every good boy does fine" and "all cows eat grass"; identifying the notes in each piano chord and trying to play those voicings on the guitar. Eventually I bought a copy of Ted Greene's "Chord Chemistry" that proved to be exactly what I needed to move forward.
No, you don't but if you play solo, it sure sounds better (to my ears, anyway), to incorporate slash chords for two reasons: one, it ensures smoother voice-leading and two, the chords more closely follow the melody. These are subjective preferences, of course. YMMV. Also, varying voicings instead of just hanging out on one voicing for an entire bar can keep things sounding fresh. As can judicious use of diminished chords. BTW, most guitar playing buddies of mine have steadfastly refused to learn any theory. They've just played the most vanilla root voicings and believed anything else is up to the bass player. My efforts to try to get them to appreciate what slash chords can contribute have come to nought. You can lead a horse to water but . . .