Do sill/wedge incisions on thinner nostrils result in 2mm reduction more significant than with thicker nostrils?

The nose pictured is a good candidate for alarplasty with combined nasal sill and Weir incisions. The proportions of the nostril width and tip width is important for the surgeon to consider when designing the incisions.

Based on the proportions of your ala and tip, you're not a great candidate for alarplasty alone. The nostrils would likely lose their natural curvature and would actually result in the tip looking less defined, not more. A minor revision rhinoplasty could enhance the aesthetic of your nasal tip...

The truth is a combination of external and internal incisions will create the most significant narrowing and reduction of flare. Paramount to success is preserving a natural amount of curvature so that the nostrils don't appear "pinched" or "stuck on" while balancing the width of the nasal tip.