Can someone help me fully understand rhythm. To my understanding as a new artist, Songwriters have focus on 2 rhythms at a time during composition. 1. The rhythm of english using metric feet, and 2. The musical rhythm using musical notes. Can these 2 rhythms co exist or are they the same?
In English prosody, the metric feet reflect stresses rather than durations. There's some flexibility of how this gets mapped into musical rhythm. It can be rather direct and unsubtle, for example in the Genesis song Colony of Slippermen which opens with a paraphrase of Wordsworth in iambic tetrameter maps each iamb into a eighth-quarter rhythm in 12/8, but by no means is that the only way to turn iambs into musical rhythm. In general, iambs are a sort of default rhythmic foot in English verse and you'll find all kinds of handling of them in different songs, although not all songs (or even most) fit into conventional verse prosody.
I have to confess that I rarely think about prosody when I'm writing songs, although picking one of mine that's come to mind, it is (mostly) in iambic tetrameter (there are a handful of anapests required for the words). Long notes usually coincide with stressed syllables but not all long notes are stressed nor are all stressed syllables long.
You may find it instructive to take some lyrics and work out the scansion in them and then see how that corresponds to the musical rhythm.
Don't really understand what you mean by the rhythm of english using metric feet (are you refering to the rhythm of english lyrics?), but in most situations, the rhythm of the lyrics is different from the rhythm of chords.
You can imagine lyrics as the melody (the one you play on right hand in piano), and chords (the one you play on left hand in piano). To make things simpler, lets call the melody right hand and bass as left hand.
The reason why the rhythms are different for left hand and right hand is to have a sense of independence and to bring out more harmony between the melody and basses. Of course, playing both hands at the same rhythm is easier and still work well, but it'll sound boring will sound like some marching song (bass always track the root of whatever chords is being played).
Additionally, time signatures also play an important role in deciding the rhythm. However, not all time signatures demand a change in rhythm. Certain time signatures can sound similar to other time signature if the tempo is different.
Example is 3/4 100BPM rhythm is almost equivalent to 4/4 130 BPM. 12/8 120 BPM rhythm is almost equivalent to 4/4 80 BPM.