Hi,
Are standard vias plugged automatically or is there an option to do so? Additionally, the design rules for 4L 35um ENIG states a min via drill size of 0.25mm? So do i need to specify my via hole size in KiCad as 0.25mm than?
BR
Hey @hardware-altavo-eu , welcome to our community 
Regarding your question on via treatments, standard vias are neither plugged nor tented automatically in our standard pooling service. If your project necessitates plugged or filled vias, we can provide an individual quote based on your requirements. Please get in touch with our support team to request a quote for this service.
The minimum via drill size for 4 Layer 35 µm ENIG is indeed 0.25 mm. You should only use 0.25 mm if your design requires that density - otherwise, you can use any value up to the maximum via drill size of 0.45 mm.