Always somewhat dubious about these GPS Apps as most of them rely on your phone to operate - using data (unless you've downloaded Google maps to use offline)
Much prefer to use my trusty Garmin that never goes wrong!!
Came across https://calimoto.com/en
You can set twisty or super twisty roads as well as normal roads, highways and motorways
Set your start point - set your finish point - select road type and it will sort out the best biking route for you.
A feature I particularly like is the Round Trip option .....
Set you start point - set the mileage you want to ride - select ride type (normally twisty) - let the App plan a route for you.
Start it from home and its suprising what new roads you can discover.
Big benefit (for me) is that you can save and export the route as a .GPX file then import the same file into Basecamp and download to your Garmin device
Give it a go - recommended
And it's free - you can go for the Paid version but why bother? Does what it says on the tin