I have seen a lot of references to the Derby Extra blade (and it is in the subject header) but many are probably referring to the pre 2016 blades. The post 2016 blades were sharper and much better performers than the pre 2016 blades but still below in sharpness in comparison to other blades. Here is the reference you may wish to read; Comprehensive Double-Edge (DE) Razor Blade Data Table - https://www.badgerandblade.com/forum/wiki/Comprehensive_Double-Edge_DE_Razor_Blade_Data_TableWell, I can imagine that, because, technically, I had great success with the Derby as well. The armpits were incredibly smooth. But the legs were quite bloody, so both my best and the worst results with a safety razor were achieved at roughly the same time thanks to the Derby Extra blade.
The Derby Premiums were an even better blade, I hear.
The post 2016 Derby Extra are 0.09mm thick and comparable to many other blades thickness' in the market so you may have the post 2016 blades. However they are no thinner than most other blades.
With regard to trimming the tabs, I would not recommend it as that is where the strength in bending lies. If the tabs are a problem choose a razor that has an extended cap which covers the tabs. Some caps bend the blade a lot more than others.