What's in the maps looking to purchase

Yes to all those questions. In fact these are very good questions so whilst we don't typically offer tech support in the Forum I'll happily answer these pre-purchase questions for the benefit of anyone else reading this that is also wondering the same:-

Specifically you're asking about road styling and custom vehicle size settings.
The Traveller app caters for this as follows:
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EOTopo 2023 Road Line style:
A solid road line (yellow for motorways but red for all other roads) indicates a sealed road, whereas a broken/dashed line in red is unsealed. It's as simple as that.
Road line thickness varies with the thinnest road lines indicating minor track to the thickest road line meaning Primary road. Any other road style colour will have text to explain its meaning:-

Tracks with dashed red & white will state 4WD only
Tracks in very pale "red" will state "Private"
Track in light "brown" will state "Permit Required".

At low zoom you will possibly also notice some roads appear with a dashed Red & Black - these are roads that form part of an ExplorOz Trek so this tells you there is additional information about these roads - planning info, a full offline route is available ready to use in navigation, or you can just read the extra info by opening the trek. The red/black line disappears once the zoom is increased and you can see the normal road style.

Thick highlighted black road lines on the map are the ExplorOz Treks. You can use the Map Layers to turn off this layer but if they're on, you can tap these lines and go to the Trek info. You can also apply filters to show Treks based on suitability - eg. 4WD only, 2WD suitable, motorhome suitable etc.
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Custom Vehicle/Rig Size Settings
You can configure your exact rig dimensions - height, length, width and this information is then used by the auto route calculator when it offers computer generated routing options from point to point. In the app, open Settings - Navigation - and set your vehicle dimensions.
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To set a route to avoid unsealed roads again, open Settings - Navigation - Exclude from Routing - and you'll have the option to select Motorway, Toll, Ferry, Unpaved. Select Unpaved and then all your routing options will be on sealed roads.

By default the app has no exclusions for navigation but you will be able to investigate the suggested route on the map and discard or adjust the route provided you don't like what's offered. To do this, you can insert other waypoints (Places) to steer the route via locations you determine. But by default the app will offer routing that goes the most logical way for the selected mode of travel - ie. Fastest, and/or Quickest. it will also use current traffic data to make that calculation to avoid current delays.
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If you have any more personal/specific questions it is best to raise a Support ticket in the Help Desk please. You can use the About page of this webpage to find the Help Desk link and other contact options. There is also a dedicated info page about the Traveller app here https://www.exploroz.com/traveller, plus you can review the mapping https://www.exploroz.com/eotopo.