The Museum of Modern Art opens a blockbuster “Matisse Picasso” show in a couple of weeks. But MoMA is in a much smaller space (in Queens)than its longtime Manhattan home. Crowds “promise to be larger than anything the site has yet encountered, raising inevitable questions about how visitors will move through the building without clogging it and whether they will have room to appreciate the nearly 140 works by two of the 20th century’s masters.”