The bialy with cream cheese is defined by what the bialy is not: it is not a bagel, and the difference is the whole sandwich. A bialy is baked, never boiled, so it has no glossy set crust and no hole. In place of the hole it has a depression in the center, and pressed into that well is a paste of cooked onion, sometimes with poppy seeds. The bread is softer and chewier than a bagel, more like a dense roll, and it goes stale fast because nothing seals it. That soft, onion-centered, ungainly crumb is the thing the cream cheese has to work with, and it asks for a different build than its boiled cousin.
The craft is in the split and the timing. A bialy is at its brief peak within hours of baking and is meant to be eaten that day; this is a sandwich with a short window, not one that survives a commute. It is split through the equator, and unlike the bagel question of toast or no toast, the bialy is usually warmed or lightly toasted, because gentle heat revives a crumb that stales quickly and intensifies the cooked-onion center that is the bread's entire flavor signature. The cream cheese is spread thick across both cut faces, edge to edge, doing the structural work of binding a loose crumb and the flavor work of carrying a cool, tangy counter to the savory onion well. There is nothing else required: the onion is already in the bread, so the cream cheese is not competing with caper or lox or tomato the way it would on an appetizing build. This is the plainest expression of the form, the bread and one spread, and it lives or dies on the freshness of the bialy and the quality of the schmear.
The variations are small because the bialy is so particular. A version layered with thin-sliced tomato and red onion borrows from the appetizing playbook; one with butter instead of cream cheese strips it back further; the bialy also stands in as the carrier for a fuller lox build. Those belong to the broader bagel and appetizing family rather than crowded in here, each with its own balance and its own article.