To add, I do not agree that Altai to Uliastaj is a good gravel road. Only the part near Uliastaj is reasonable.
The rest of the road is either swerving or has stones or holes or whatever. It can be done, even with a Prius, but the average speed is low so you will spend most of your day.
I am talking about the red road in Open Street Maps.
It may not even be that bad to go from Olgii pretty direct over Khyargas lake, but there are parts where it is hard to find the right track and so on. Scenery should be nice.
I was not that impressed by the scenery from Olgii to Altaj.
Khar Us Nuur was nice. And we went to Chandmani because of the Mongolian throat singing.
The roads to and from Chandmani were not that good obviously, as expected, but even they were not slower then from Altaj to Uliastaj :P
Also went to Dorgon/Durgun nuur, where on the east side the sand dunes meet the water, quite nice.
Now we will head into Zavkan with some tracks probably also driving in sand tracks etc. Then join the middle route and see how much is asphalt
As said from Khovd to Altaj is very good asphalt. Between Olgii and Khovd is not finished yet so that takes time. In 2019 probably very smooth.