#1
I'm learning some songs, and some of them have obscure chords that i have no idea how to play. one is something like E/#F. Could I play just an E chord instead? or would it be too much of a difference?
#2
Not too much of a difference, but that chord really isn't obscure. Any time you see a / in a chord name, it's telling you what bass note to play, so a E/F# would be an E major, but with an F# bass. One fingering of that would be: 222100
Hi, I'm Peter
#3
Slash chords can usually be changed to the bass player playing the note to the right of the slash and the guitar player playing the note to the left of the slash.
#4
To answer the original question, Yes.

If you see a chord, all you need to play to get the tonality of it is to play the implied triad (Major or Minor, maybe diminished if It's there). So if you see an Aadd9/B, it's safe to just play your open A chord, the Bass usually picked up the B in the bass and the 9 is just an embellishment.