Use Android Auto.
This will reduce the accessing time for Maps or Any other application required while driving. Also During driving and using android auto, you'll have a better experience of Map as the notifications from other apps won't bother you as they do on running the Maps app directly.
Reason for this is to minimize the interruption of other apps ...
For me (Android 6 on a Sony phone), "screen pinning" does this, with no need for third party apps.
The option for me is in "Settings", "Security", "Screen pinning", which you set to "on". You pin an app by swiping up on it from the overview list, then clicking the "pin" icon which will appear. To unpin a pinned app, press and hold the "back" and "overview" ...
How about using NFC to tell the phone that it should switch itself to driving mode when inserted into the cradle?
You can get nfc stickers for few euro/pounds on ebay..., put one to the back of the cradle, setup your phone and off you go :-)
That probably isn't what you're looking for but still, it's nice and elegant solution ;-)
Go to settings > language and input > text to speech output.
There you can select one of your installed voices.
You can install voices from the Play Store.
My personal best and free is IVONA (https://play.google.com/store/apps/details?id=com.ivona.tts&hl=de)
You may need an additional tool for Speed Camera alerts or an alternative navigation tool with built-in speed cam alerts feature.
For the former, there are some options from playstore but ideally you'd still want to keep Here WeGo so you could go for an application with an overlay support/widget that ensures you use your primary navigation app whilst still ...
Go to the phone Settings. Click Display from the Device group, then on the next screen click Notification panel. You can add and remove notification bar items from there.
Not all Samsung ROMs have this option: in particular, I don't think the Galaxy S III had it until 4.1.2.