I think it is always risky to wash a quilt top, so I would avoid doing that if at all possible. Unless you live in a tropical climate or intend to store the quilt top for years at a time, it should be fine to leave the starch in the top.
There are so many different ways you could store the top, it would be hard to describe them all. If it's a large top and you want to avoid a lot of ironing later to get creases out, you can wrap it around a length of PVC tubing (big tube rather than smaller tube, for less distortion. Otherwise it would be fine to fold the top.
Storing inside a rigid plastic container is fine, although small quilters worry about long-time storage this way because of gases emitted from the plastic. For anything a year or less, I think it's fine. (Some of my fabrics have been in rigid plastic storage bins with covers for years and show no signs of deterioration.)
If you wrap around a tube of PVC, I would enclose the quilt in white cotton fabric to keep dust off and let the fabric "breathe". That is probably the ideal, although it won't protect the top from water damage (if you have a flood, for instance).