Does switching my GPU to MSI mode actually help?

For FPS, no. You won't see the number move in a benchmark. What it can help is latency and odd stutter, because the card signals the CPU differently and stops sharing an interrupt line with other devices. If you get random hitches or crackling audio, worth a try. If everything already runs smooth there's nothing for it to fix. Two things: a lot of newer cards already have it on, so check before you change anything. And a clean driver install puts it back to default, so you have to set it again after updates.