Help how can i delete or edit my sync data ?

[Gaia]

Hi
sorry i'm not sure android application is not the right place to ask this question
but i can't find a subforum suitable

i own a samsung s5 and a s3 mini , but for example my friend owns a nexus

well
in my mobiles in the sync features i have a samsung account and google accout

on both my mobiles i have the sync enabled

now my questions

1) how can i remove the cloud data in the samsung account and google account?

i was able to login to my samsung account via desktop firefox , i can not delete for example s memo , s note (143KB)

2) about google account how can i check via desktop firefox my data synched ? manage , delete ?

please my english is poor
thanks in advance!
thanks