7.4 is fine.
Some fish prefer soft, acidic water with pH below 7, and some fish prefer harder water with pH above 7. And this relates to fishes natural environment. But most fish are now captive bred or farmed, and not coming from water that matches their natural environment, so unless you are buying wild caught fish you are better matching the water they have at the fish store.
Corys generally prefer water in the 7 to 8 range, but it really depends on the specific species. If you are between 6.5 and 7.5 that's a good range for most corys. Having a pH of 7 will cover a lot of bases for a lot of different species of fish though.
Tetras generally prefer soft acidic water, with pH below 7. But as said most fish are farmed or captive bred, and many people keep tetras in harder, higher pH water. Same for bettas.
I've kept tetras, bettas and corys in water pH similar to yours.
Keeping pH stable is much more important than what you might consider an ideal pH. If the water at the store is significantly different to what's in your aquarium you want to have a good acclimation process to adjust the fish from one water type to another.