You can cut your peony back or just let the top growth die over winter and then cut it back. It probably won't bloom for a year or two because you moved it...they resent movement and usually sulk and don't bloom for a while.
If you use mulch to protect your
roses, be sure to pile it up over the graft line. I've never tried using a bucket, but then it doesn't get as cold here.
Once again you can cut your perennial hibiscus back or just let the top growth die. They are slow to come up in
spring, so you should mark it so you don't accidentally dig it up or something.
You can prune your
rose of Sharon to keep it from getting too big or just to keep a nice shape.
Do not prune your hydrangea...you are right in that they bloom on old wood and if you prune now you will be sacrificing next years blooms. Next
spring just cut back any dead stems. If you need to prune it, do so right after it blooms in summer.