I have reduce motion on, but have not touched reduce transparency.
I think the animations are cool looking, but I don't need that to happen all the time. Every now and then I will switch it off, but 99% of the time I have it on.
My iPod 5G is a bit slower with animations enabled so it's the same with iPhone 4S i guess since it has similair hardware.
The difference in speed is really tiny so you won't really have issues with that probably.