I have a Micro-ATX case for my PC and am a little skeptical that flow-through would well for that form factor because the intakes are on the bottom of the card.
Any temps below 80C at load are perfectly safe and shouldn't result in throttling -- the same is true for CPUs. If you aim for lower temps than 80C, you aren't going to get better performance, although lower temps are a good way to get your computer to run more quietly.
You're not directly going to get better performance, but you can run higher clocks for longer before throttling, leading to higher performance.