AusBonsai

Is Chinese quince mainly for autumn leaves colour?
Flowers not commonly seen. Not like Japanese flowering quince.

Chinese Quince have beautiful bark and often get fluted trunks.

Yes, Chinese quince are probably most valued for the trunk and bark. As the bark sheds each year the trunk takes on a leopard skin patchwork of browns, greys and oranges.
They do flower - 2-3 cm pale pink single flowers. Very nice but I have not been very successful at getting them to flower and fruit in the bonsai pot - possibly pruning, maybe nutrition?
They also produce fruit - Large golden smooth skinned fruits with a lovely aroma. they taste great when cooked and make the most wonderful quince jelly, etc. Not recommended to allow bonsai to develop fruit as it takes a great deal of energy from the tree. They are sometimes shown in Japanese exhibitions with fruit but these have almost always been taken from a garden tree and tied in place just for the effect.

My Chinese quinces don't ramify very well so the bark and trunk seems to be the best attributes as bonsai.

Ground-growing can get good thick trunks with interesting angles quite easily - the scars from large branches can add to the effect.

Gavin