Hi the best and smooth route is NH44 up to maneswar and take peripheral expressway so that no need to enter Delhi and exit at Rai from peripheral way towards panipat again NH44 until ambala. from ambala take right towards rupnagar n that ll lead u to manali thus you can bypass both Delhi & Chandigarh. however probably you seeing the jodhpur Jhunjhunu route which merge at Ambala, that road is also fine but NH44 is more running and smooth highway so suggest take NH44 Thank You
See You on the Road ...👌👌
From Chandigarh its 8 hours and from Delhi its 11- 12 hours. From Delhi you will get plenty options - Cabs, Local buses, private buses too. Chandigarh there is Govt HRTC buses available but they have fix timings. Google for more info