Heres My Approach for your tree,
But firstly let me answer your questions:
Proportions I think are mostly personal taste and in your case (eg. Species I think the trunk is appropriate size), since Blue Atlas Cedar Commonly grow a relatively thick trunk, you can see that here:
Also stylewise you really have a good structure going on. Since naturally the Grow in quite a "Top-Dome" shape, with wide, round branch pads layed out.
Me Personally I would develop the Apex as is, I think especially for that size of tree It looks really nice.
Now for my personal styling advice.
I think you choose a great Front, since the tree leans slightly forward, engaging the viewer.
Lets begin from Top to bottom.
Firstly, the white circled branches, I would either remove and heal over the wounds or make 1 or 2 to jins.
Your choice, however I would remove them and let the tree heal over.
Secondly, the yellow circles areas.
I would give them firstly a rough wiring, with a bit of subtle movement, not to much and to drastic, and also a slight downward movement.
Also remove the growing tips on the top branches, to firstly get elongation of rosettes more narrow to the trunk on the branches, since these will help you over time build nice pads, like on our reference tree
If you do this work (cutting back tips, wiring young wips in fall) repetively the branch pads would look something like this:
The light blue circled Branch I would personally let grow till it reaches the state that it can be build as a branch pad to.
Then to the green area, I couldnt really see where the bulge comes from, but I would remove it, if its the rest of a old branch.
Now the Orange Apex area, I would go a similar approach then the yellow branches, cut back any outgrowing branches as they harden of over the year, to get more ramification and fill out the crown, but personally I wouldnt make the Crow much wider than 5cm ~ 2 inches than it is now, this will also hide the red stump up on top, which I would carve out / chop down and try to let heal over.
The branch on the down-right (on the apex) I would use as the outer boundary of the apex to the right, since we want a slightly asymetrical top.
In the meantime work on the nebari and creating a good root base.
After 3-5 Years of repetivie work on the tree, you will have a crown and branch structure rougly like this.
And it is basically ready for a new pot.
Of course in a much smaller scale and other style / angle than this tree.
Also the branch on the left of the apex you used for building the crown will be hidden by the new foliage.
May I ask, where the tree came from (size wise) and how tall it was.
Please also ask yourself these questions before working the tree (any cutback or rootwork), since atlas cedar are fairly sensitive
Is the root system healthy?
Was the growth of last year adequate / relatively vigourous?
if you can please provide me with some more pictures of the trees current state, and some other angles and photos, I can refine my work...
Also a photo of the graft would be good, to see if work has to be done there and maybe if we leave a few lower branches to grow it out...
For now thats all I can say.
Hopefully my answer can help you and is still relevant to you, since you posted a few months ago...
So far I can only say, you tree is on a good way to becoming a nice small / medium bonsai.
Honestly Ive never seen a small atlas cedar like this, however I really like the look of it.
Have a nice day,
Greetings from munich, germany
Waiting to hearing back from you
Cheers
Raffael
