What changes once the open chords stop being the hard part.
If you can change between the common open chords without stopping and hold a steady strum, you're ready. Intermediate songs mostly add 7th and sus shapes, the occasional barre chord and strumming that varies through the song instead of staying flat.
It flattens one finger across several strings so a shape can move up the neck (my bar chords guide walks through it) and Bb is usually the first one people meet. Barre chords feel impossible for a week or two and then suddenly they don't. If a song calls for one, the transposer can often shift it into friendlier shapes while you build up to it.
Practice the change rather than the song. Take the two chords that trip you up, swap between them slowly for a minute and keep your fingers close to the strings. Speed comes from moving less, not from trying harder.
Often, yes. Use the transposer to move it into shapes you already know, or flatten the rhythm to one down-strum per beat while you learn the changes. Put the real strumming pattern back once your hands know where to go.
