Are these actually IN an apartment?
This is a great start of a piece, so good if it IS indoors I'd sell it to someone who could keep it outdoors for the betterment of material and high quality trees all together.
I think your goal of a mame is a righteous one, but I don't think your current path will get you there.
I agree there is little right or wrong with styling, however, with such a tiny goal, flaws that make any goal impossible are amplified.
The flaw I find in this, as many others, is this prominent initial trident that has been left to grow exactly as nature intended, perfectly straight, and utterly boring.
This look will continue to make the viewer see this as "an attempt", or "a bonsai", but never a "real tree in miniature".
The difficulty is even after removing any one of the three legs of the trident, it remains "fake looking", just without worry of reverse taper.
So I propose that in order to make a convincing mame, you may have to regrow new branches from *where the first ones currently are*, or better, use some that may sprout lower.
IMO, the first nodes on those first branches are entirely too far. Also indicative of merely a healthy seedling, not an old tree.
You can't both rely on internodes that long AND have enough nodes to create branches on a mame sized tree. It is mathematically impossible. Unless your tree only has 3 branches, but that's a fail IMO.
So the reason your path doesn't line up for me, is because you have a LOT of development to do. Development that will require more pot than that small one.
No worries though, because as
@Shibui notes, they can take quite the root removal, so getting it into a right small pot in the future shouldn't be a worry. I believe your climates may be similar as well, so following his advice is probably really true.
My first move would be cutting out the center trunk and looking for lower or better buds.
"Better" buds....*where the first branches currently are*.
Healthy maples, as this has been, will throw six buds at each node, 3 on either side, one Central or "apical" branch, that the tree naturally uses to quickly expand into new territory and make "sub trunks", these are mostly useless to design, and it seems are the ones your young healthy tree gave prominence to.
The smaller side buds are "reserves" for the natural tree, if nature decides to remove the trunk extension, die to lightening, pests, or even a neighboring tree that shades the large extension that then makes for more possible sunlight back at those close short nodes.
The idea of that cut is to sprout them side nodes from where your current "ugly tell branches" emerge.
The difficulty in this scenario is the future removal of the "ugly tell" branches, as the wound is very close to the young small, closely noded branch you wish to keep.
This is why it would be better to utilize lower growth (grafts if you're gangster) which you can keep from ever giving you the difficulty of this prominent trident shape.
Prominent trident shapes are the bane of a good maple and must always be prevented.
Removing the "tell" is always more difficult than preventing it.
Sorce
