In the new brush interface, there seem to be a bug where if one changes the engine, then the options does not change or at least it can be perceived as a bug. For many people, clicking first on the engine, and then the brush isn't really acceptable as it slows down their workflow. There's a thread on the KDE forum that I have started, and it appears that I'm not the only one who don't find this workflow acceptable, and would like to see v4 act like the 3.1.4 or at least it should be a option.
I am using Windows 10 x64. Had to add this as I didn't mention this before.
See https://phabricator.kde.org/T7380 for a discussion on what selecing a brush engine should mean.
Could you put a link reptillia to the discussion. I think people would be interested to hear about why that work flow is good. I don't know why it would be useful outside of the developer use case
Here's the discussion - https://forum.kde.org/viewtopic.php?f=139&t=140758 Some people like having to click on the engine, and then all the options are there, and the default brush are automatically assigned to the engine. Just like the old Krita. Other people hate it. For those who hates it, they have to delete so many brushes, and assign names like "1 - Pixel brush" "2 - Smudge brush" To get the old Krita feel in that aspect. A hybrid approach may be needed here. The better approach would be: One should be able to change brush engine, and the brush used automatically changes. But, the selected for each engine is automatically used. This is the hybrid approach to accomodate as many people as possible.
Since I can't edit - Replace "Other people hate it." with "Some people hate the new approach."