Where does it say that one shouldn't eat foods like sandwiches or pizza and hold the food in one's hand and bring it towards there face, but should rather eat in smaller bites or with a knife and fork. Who are the poskim that say there is no problem of this nowadays (and perhaps that it's considered to be the way people act)?
Beis Yosef to Tur O.C. 170 s.v. לא יאכל
לא יאחוז פרוסה כביצה בידו בפעם אחת והעושה כן הרי זה רעבתן ומשמע מלשון הברייתא שאם אוחז פרוסה כביצה אע״פ שאינו אוכל אלא קצת ממנו נקרא רעבתן
Do not hold a piece the size of a beitza in your hand at one time, and one who does so is a glutton. And the implication of the Baraisa is that if he holds it, even if he only eats a little of it, he is still called a glutton.
Dayan Yisroel Fisher held that this applies in full, and is objectively gluttonous, and therefore one should not hold a slice of pizza, a bagel, or a sandwich without cutting it into small pieces.
Shu"t Orh L'Tzion 2:46 says that if it is the normal way to hold such a food then it is not a lack of derech eretz. In V'zos Haberacha, Rabbi Mandelbaum reports that he asked many modern poskim about this issue and they agreed with the Ohr L'Tzion, but he does not name the poskim.
In V'zos Haberacha 2:4 footnote 3, he suggests that the volume of a beitza was set by Chazal because their bread was much denser, and therefore a k'beitza was much more filling. Today, our bread is much fluffier and it is not gluttonous to hold that amount, and a larger amount would be more relevant (he does not specify what the larger amount would be).