That is up to you. I only did my lows. I can see better with my lows now (w/ HID) than I could see with my stock lows and highs on. I didn’t feel the need to make my high’s HID since the lows are so bright.
I got a 55W kit as opposed to the 35W. The 55W are way brighter than the 35W kits. I also got 6000K bulbs. 5000K are supposed to be pretty close to stock coloring, the 6000K have the slightest blue tint to them (not the ricer blue or purple). I would go with either 5000K or 6000K.