It is possible to install and start both wicked and NetworkManager. Since
wicked is the default this is the case in most situations when you install NM.

When you don't disable the wicked service before starting NetworkManager it
starts and connects to networks but does not update resolv.conf

This is probably related to only one of the daemons owning the network service.

However, if NM wants to not run when wicked is enabled it should not run at
all. If it runs it should provide all services,  including updating resolv.conf