Can different phrases be related to a same noun, modifying it and how to avoid ambiguity? E.g I remember man playing guitar that (this clause is related to "man", not "guitar") sounded good
Yes, they can, but there is no reliable way of avoiding ambiguity.
A possibility that sometimes works is start a new breath group (represented by a comma):
I remember a man playing a guitar that sounded good (probably the guitar)
I remember a man playing a guitar, that sounded good (probably the playing).
But even then, my "probably" indicates that these interpretations are not forced, in either case.
Note that I have inserted the articles which you omitted, and which are required in English.