There is no “best gear ratio” - that’s on you to decide what you want your gearing to be. For your 480 2.75 comparison to 3.25 400, they are actually at about the same speed ~(68 in/s). Most teams I’ve seen have around that same speed. As for 3 wide, it’s possible on drivetrains - its more difficult for some since the gears might not fit into the wheels. For 480 and 400, you might need to change the 48T gear as well - check your spacing Using ls and hs gears is at your own discretion - I would say whichever one has better meshing with how it’s positioned is better. Hope this answers your question! If you need any other advice, I would recommend looking at this post. Posting pictures of your CAD may also help us understand.