I've never found any real use for corvettes or destroyers, if I'm being honest. They're only really useful early-game for zerg-rushing your opponents and scoring early victories. For actual war, I rely on cruisers and battleships mainly in the configurations I mentioned. I also like to do super fast tech-rushing and outclass all the AI as quickly as possible. When I play, my real enemies are Awakened Empires and the End-Game Crisis - everything else is just fodder. Once you figure out just how inept the AI is, the game very quickly becomes mind-numbingly easy and the only way to get a real challenge is just putting the difficulty up. I'm not saying I'm amazing at the game, but once you've got a solid tech-rush build figured out then the AI just can't compete.
As far as tech goes, Fallen Empires have 10x repeatables (all repeatable techs) so they've got some crazy bonuses to their weapon damage, armour, shields, firing speed... The whole spectrum. That's what makes them so scary if you're behind on tech. I like to rush so I can match them on tech and then just out-class them on numbers. It's a lot easier and quicker to get to those really crazy levels of research on PC because of the features it has over the console edition just now, such as relic worlds and specialised habitats, so I wouldn't pay *too* much attention to Aspec's tips. A lot of them simply don't transfer well from PC to console while the two versions aren't at parity. But no matter what system you're on, I've found that the most overpowered thing you can do is rush those researches to a ridiculous level. I can get well into the repeatables by 2300 normally - or by 2270-ish if I get a good start, good planet spawns and optimise well. Play tall, stay within your empire sprawl and bully your neighbours into becoming tributaries and focus your planets solely on research and alloy production so you can advance quickly and build plenty of ship. Do that and you can't go far wrong.