Transfer apps and settings to new smartphone Moto G android 5.1
I have bought an Samsung S5 neo, running on android 6 Marzshmallow.
To have all my current apps (in Moto G android 5.1) with their settings in S5 neo, it is actually as simple as to sign in my google account with the new phone or what should I do the simplezst way?
For photos, videos and docs in general I already made a back up in google drive.

Many thanks
No, that might not cover all apps. Though the apps themselves might show up on your new device (provided you've used the Google Cloud Backup on the old one and decide to restore that on the new one), to have the apps' settings transferred, apps must explicitly support that (at least with Android 5.x that's still the case) – so from those which don't, the date wouldn't show up on your new device.

However, there is a way to transfer those data manually using adb backup. Details are described in answers to Full Backup of non-rooted devices. If you're not that "command-line savvy", take a special look at my answer on that, the app Helium Backup should make such transfers easy – especially with its full name being "Helium - App Sync and Backup" :)

Still, some apps might have "opted out" of being backed up (developers can specify that) – in which case you'd need root to accomplish a full transfer.