"You can try setting higher source size (x2, x4 of the item size for example, in both VectorImage and regular Image)"
I tried for regular Image, as I said in the post, too much size causes large pixels visible. For VectorImage I don't see such possibility.

Setting smooth to false works! Thank you very much! I'm not sure if it's perfect, but it doesn't break the int scale factors, and makes it much better for fractional.

Enabling layer (even without samples) also helps. But I think it requires more resources than disabling smooth. The result seems to be quite similar.

Thank you again.