I now use a v2 kit with waveshare 3.5 display and a RPi 4 in a 3d printed case.
When I want to use the v4.1 case, do I just need to replace the display with the new Zynscreen 1.5 display with the new buttons? Can I re-use the other components from the V2 kit? Including the flatcable?
Your problems are more about Pi 4 form Pi 3 problems. The Sockets for the Pi have changed. USB & Ethernet has swapped places, we now have 2 micro HDMI’s instead of the original big single one and probably most significant your power supply connector is now Type C USB. So that’s your biggest change. Basically you’d have to get the dremmel out if you put a Pi3 in a v4.1 case.
I already have a Pi 4 in my current V2 setup. The current 3d printed case is also for RPi 4 as is the new Zynthian 4.1 case.
I know I need the Zynscreen 1.5 because off the 4 new buttons in the 4.1 case. But can I use the current v2 flatcable to connect my v2 Zynthian Basic Kit to the Zynscreen 1.5?
Should be ok. But I’ve not got any direct experience having not used a ZynScreen
Personally I like my touch screen bigger but I’m an old man with a collection of lousy eyes !! . . .