Use the details option in the g-menu to see what your damage/tick is for a salvage group of any one size&support. Default every block has 200 salvage-hp that you can attack when it's in a salvageable state, weather rock, ice, or shipcores. Some servers may have modified this base number, but it's unlikely.(The {delete} menu has the same info, and some other useful things like your current power and capacity values to help with balancing a build.)
As long as the damage/tick is at or over 200 your array is working optimally. If you're below 200/tick it's best to go as close as possible to a whole-number division; 100, 67, 50, 34, and 25. This minimizes "waste" of time and energy.(2 ticks of 100 will salvage a full block, 2 ticks of 180 will salvage a full block wasting 160, 3 ticks of 67 will salvage a full block wasting 2)
No matter how awesome your array is, the server itself will determine what "maximum" salvage power is. Going past this will result in some rubber-banding in the engine as the target "catches up" to what you've done in chunk-updates.
Using missile-slave gives you an extra sweep of beams to salvage a wider area, like a planet plate.
I think the update to the basic salvage beam made cannon-slave kinda nerfed. they already have a default 0.03 refire un-enhanced last I checked.
Beam-slave is good for if you're fat-and-slow. letting you harvest stuff from a distance without having to maneuver much. or to keep it outside a gravity-well.
Pulse lets you have smaller arrays that "burst" a bit better, but have long cooldown in-between shots. I'd only use it on a ship that can't afford to be a main-line salvager. something like a skirmish-and-salvage ship, fighter or whatnot.