ABEC ratings have nothing to do with speed or anything else to do with skateboards or skates. Actually, the higher ratings could be slower.
The ABEC rating is for smaller gaps between the parts so that they do not vibrate in high speed machines. You won't be into the range that the specs relate to until you are over 200 mph.
Some of the top makers of skate bearings (Zero Drag, Twin Cam, Bones) have designed their best bearings to have larger gaps in critical areas to roll faster but the gaps mean that they don't even meet the ABEC 1 standard.
The lubricant used in a bearing will have more effect on it's speed than anything else. Light oil is fast but you need to add it more often. Grease will last for years but is sluggish if more than a tiny amount is used. Gels are in between.
Unless you have extremely different bearings (like oil vs over greased), your wheels will have a much larger effect on your speed than the bearings.
15+ years of inline skating - 30 years of engineering