A 400 grain arrow moving at 262 fps should be generating about 60 to 61 foot pounds of kinetic energy. That should be fine for use with expandables but by all means make sure your bow is well tuned. Don't just use an expandable to get your field tips and broad-heads hitting the same spot. You will get much better performance from expandables if your bow is tuned well enough that you could shoot fixed heads if you wanted to.

Typically the rule of thumb on how light you can go with arrow weight is to maintain at least 5 grains per pound of draw weight. For a 60 lb bow you could go as light as 300 grains but I wouldn't unless I could achieve it at no cost in increased noise. Heavier arrows help dampen vibration and quiet a bow down. 262 fps is fast enough. All speed gains you is a little margin for error in range estimation. And any bow hunter should have a range finder that renders range estimation to target unnecessary.

I'd far rather have a quiet bow. There is no such thing as a bow fast enough to overcome a deers ability to duck the string by pure speed alone. That is a fantasy. Now if you can get a bow to shoot 300+ fps and be very quiet, great. But I haven't found one yet and I've owned many. I'm back to hunting with my old Mathews Q2. I just can't seem to wean myself from it. Why? Because despite only flinging arrows at about the same speed you are getting it sounds like a gnat fart muffled under a pillow when it goes off. I have had deer duck the string on much faster (and louder) bows I owned but never that Q2. They don't seem to react to it at all.

So if the bow you have is quiet then I wouldn't worry about it. It's plenty fast and should blow through anything you hit. Besides speed bows often achieve their velocity by having short brace heights down around 6 inches or so. That can make them hard to shoot accurately.