Im doing research on injectors, and im not clear...

Whats the difference between low/high impedance? (not too technical, but whats the difference)
Whats the difference between peak and hold, and saturated?

And lastly, i have a 94cx civic, and a obd1 b18c1 swap, with s300. What injectors for that? Im looking for 750cc's...prolly rc750's. Any other suggestions?!

thanks!