Do the Ernie Ball Super Slinky Nickel Wound 9-42 strings have a noticeably brighter tone compared to the Regular Slinky set, and would this affect pickup height setup?

Yes, the Ernie Ball Super Slinky Nickel Wound 9-42 strings generally have a slightly brighter tone compared to the Regular Slinky set (10-46 gauge) due to their lighter gauge. This difference is noticeable but subtle. Lighter strings may also produce a bit less output, so you might need to adjust your pickup height slightly if you want to maintain the same volume and balance, but most players don't find major changes necessary.

Are the Ernie Ball Super Slinky Nickel Wound 9-42 strings compatible with floating tremolo systems, or is there a risk of tuning instability?

Yes, Ernie Ball Super Slinky Nickel Wound 9-42 strings are compatible with floating tremolo systems. Many players use these strings with floating bridges, but you may need to adjust your tremolo setup for the lighter gauge to maintain tuning stability. Proper installation and stretching of the strings will help minimize tuning issues.