As you mentioned, you're going to install retropie and use hardware buttons.
I would filter out touch screens as they tend to get expensive (but they seem to be most common to find). Additionally, look into resolution as you probably don't need 1080p or even 720p screen. 4:3 ratio could be also useful to you as most of retro games use 4:3 and it would give ...
libnss3 package provide libnssutil3.so and libnss3.so (You have already installed the required package)
libnspr4 package provide libnspr4.so
libnssutil3.so should be under /usr/lib/arm-linux-gnueabihf/libnssutil3.so