In spark strips, you need high voltage to jump the gap.
Railguns need high current, with moderate voltage (Powerlabs' first railgun used 100.000A and 3200V).
So how are they similar?
Plasma in the initial railgun you reffered to is generated by ohmic heating of the projectile, so using it without a projectile would never work at normal voltage levels in normal atmospheric conditions (or inside a chamber, where breakdown voltage is even higher). In a nutshell, a railgun cannot work without its projectile. At all. It won't even discharge.
I thought you knew these things, man

It's pretty basic.