The first example doesn't really sound authentically-Chiptune to me. The best way to emulate Chiptunes is to just use the same patches from the soundcards of old video game consoles; luckily, they've made a series of VSTs that do just that.
http://www.superaudiocart.com/
They have ones for consoles (audio cart), gameboy and PC.
For 80s-style chiptunes, you'd also want to compose with the limitations of the NES in mind. The NES did not allow for polyphonic channels, and you only had 3 channels for oscillators, with the fourth being white noise for a drum kit. This means you'd want to write contrapuntally or in 3-part harmony if you're aiming for authenticity.
For your second example, you'd want to use emulations (or the real thing) of synths like the Yamaha DX-7, Roland Juno 106, Jupiter 8 and for drums: The Linn LM-1. Tons of emulations exist of these things.
With the drums, the stereotypical-80s approach was to send the snare and toms into a freakin' massive reverb and then put a gate on the reverb so it cuts the tail off quickly.
Other than that, they added chorus and delay to many lead sounds, pads, etc.
Structurally, it was no different than modern pop music.