I understood what you are asking.
Their plan of exchanging off your fianchetto Bishop is a common pattern. Launching a pawn storm when players are castled on opposite sides of the board is also a common idea, but even if they trade off your fianchetto Bishop and castle to the side flank you are castled, they can still gain an advantage without a pawn storm.
Fianchetto openings are solid and played even at the Grandmaster level. You just have to always be careful about losing your fianchetto Bishop because you get left with "weak squares" around your King. This video of mine is a good foundation and I also have another video on the pawn storm topic you mentioned:
Hello, I am wondering what some people think about this. When I was starting out as a beginner I loved to play openings like the Reti and the Modern defense. But, as I continued to play, I soon realized than many players had a “system” that they used to crush me every time. I would fianchetto my bishop and my opponent would line up there bishop and queen to try and exchange their bishop for my strong fianchetto bishop, pretty normal stuff. But what they did after I found to be quite a pain. After we exchanged bishops, they would castle queenside and throw all their pawn at my king, open up files, and I would get mated. It seemed like this was unavoidable when playing these openings, so I promptly decided to never play them again. Recently, though, I have wanted to try to play fianchetto opening because I recalled how fun it was (at least when I wasn’t getting destroyed). So, all that to say; how do I avoid these seemingly unstoppable pawn storms, and how do I handle myself when my opponent when pushes their pawns right up to my king. Sorry if that was a bit confusing, but if anything was unclear please feel free to ask.
Thanks a lot, I really appreciate any advice!