Need a little help with "harmless" on piano

[Charlie17]

I've been "playing" piano for around 7 or 8 months now, and I am confident that I have the chords worked out, but I have a feeling he plays inversions or something and my feeble guitar oriented mind can't seem to figure it out. Piano is pretty amazing though. Love it, but it's frustrating to hear he's playing a Gmaj, Amaj, and Fmaj(add9) yet it doesn't quite sound the same. I tried scouring the piano section. any help would be appreciated. I can try to return the favor somehow if possible via guitar although i doubt there are many mysteries left to be solved.

[Charlie17]

If i were to play it on guitar. I like the sound of a G6 chord, with the shape of 3-5-0-4-0-0, in standard tuning. followed by an A played as, 5-0-7-6-5-0 followed by what's an Fmaj7,

1-3-3-2-1-0. doesn't seem to translate to the keyboard though