Re: 80s guitar sound (what are the characteristics?)
I don't know if there's a defining 80's sound, but I think what you mean is 80's metal like Scorpions, Judas Priest, Iron Maiden, Van Halen, Ozzy, Dokken, etc.
That sound is the JCM 800/Celestion G75T's/Boss OD/Seymour Duncan JB, 59, or Custom.
The DSL's, TSL's, Jubilee, Splawn, Roccaforte are the right amps to get that sound. It's tight on the bottom, neutral mids, and crunchy highs, with most of the mids coming from the pickups.......which is why Duncans like the JB were popular.
In the 90's, the tone shifted more towards the Mesa Dual Rec sound, so if you like the tone of Ozzy/Judas Priest/Scorpions more than Limp Bizkit, Linkin Park, and Nickelback, then you're after the highgain Marshall sound.
There's no real EQ tips. You need the right amp, and the DSL50, JCM800 or 900 with a 4-12 is the most surefire way to get it.