Mounting samba shares with this method, https://wiki.archlinux.org/index.php/fstab#Automount_with_systemd gave me some freeze when accessing samba shares when it has been disconnected. Using systemd timeouts does not help : https://bbs.archlinux.org/viewtopic.php?id=225973 .
As an alternative, using https://wiki.archlinux.org/index.php/NetworkManager#Network_services_with_NetworkManager_dispatcher gives some good results : no freeze when shares are offline.
For Samba configuration refer : https://www.tecmint.com/setup-samba-file-sharing-for-linux-windows-clients/
In order to be able to write on shared drives, either configure samba with create mask=0770 Force create mode=0770
or add it to fstab
//a4h-rpi-dev-remi.local/rpi_projects /mnt/partages/a4h/rpi-dev_projects cifs _netdev,noauto,credentials=/etc/samba/credentials/a4h/rpi-dev_projects,file_mode=0777,dir_mode=0777 0 0