Does authentic Italian tiramisu contain large amounts of espresso?
A typical tiramisu will serve a good number of people, so each serving is unlikely to have more than about a shot's worth of espresso. There's a limit to what the savoiardi will absorb so you'd struggle to get more coffee than that into a portion. Further, the flavour is diluted by the flavour already present in the savoiardi as well as the alcohol, mascarpone, cocoa on top and other ingredients. I wouldn't worry about the coffee flavour overpowering the rest. Obviously if you've made it before and felt the coffee was too strong then reduce the quantity.
Note that in Italy, caffè will by default refer to espresso, or at home to the product of a Moka pot or equivalent. Filter or drip coffees are not a native part of Italian coffee culture (hence the americano, imitating filter coffee by diluting espresso). You could search for older recipes in Italian (although according to Wikipedia, tiramisu is not an especially old dessert) but they will probably just say caffè.
Remember that tira mi sù means 'pick me up', alluding to the fact that the dessert contains enough coffee to wake you up a little at the end of a meal.