You can swap around the type of meat used, without much issue. I have exchanged the 1 pound of pork for buffalo or the lamb for veal without any issue. The meat listed is my own personal preference, but I will swap it up with what is available when I go to make it.
I usually make one loaf pan and 4 - 5 mini meatloafs on a sheet pan (because my husband likes to slice it for sandwiches and I like lots of crust on an individual loaf). So it leaves a lot of options, but likely it would be either 2 loaf pans or 2 sheet pans.
For the sauce, you can use ketchup instead of the tomato paste. The tomato paste makes it a little thicker of a glaze. Sometimes I will "thin" it with ketchup, as mood fits.