Is that what that recharge bar is for, next to the weapon indicators in game? I thought that had to do with heat.
"somehow". powerdistributor is distributing power to system, engines or weapons. formally it is distributing power for thermal cooling of the weapons, so it defines how long you can fire your weapons, before they overheat (or run out of ammo). while you fire a weapon, the bar next to it gets emptied, if not refilled by the powerdistributor in the same time, and weapon will show "thermal overload" and you can't fire it. class and quality of the powerdistributor define its recharge rate and the amount of thermal cooling power it can store. so, if i was writing above, a 3A powerdistributor can sustan a medium beam laser nearby endlessly, that means its recharge capacity is big enough, to give permanent cooling to the beam laser.
on the other hand you have a heat indicator on the left side of your hud. it shows heat of your ship in percent. at 80% you get a warning, at 100% you get a "taking heat damage" message, and your moduls will take heat damage, and at some point above that, your hull will take heatdamage, too. every module turned on produces an amount of heat, the more power it uses, the more heat it produces. beam lasers need a lot of power, so they produce more heat if deployed, whether they are fired or not - after deploying hardpoints your ships heat should rise. if you fire your beam laser constantly, this produces more heat and adds to it.
but this isn't a good reason to stay away from a viper. people complaining about a vipers heatmanagement will have fit a lot of high power usage moduls turned on in combat, like shieldcellbanks, shieldboosters, lot of beams/ plasma-accelerators/railguns... in a reasonable outfit, with turning off unnecessary moduls like cargo hatch, or fuelscoops, you shouldn't run into problems.