For another perspective and more details, RenderDoc (or another frame debugger if you have one) is a nice tool as well.
Also don't use Rectangle { color: "transparent" }, use Item {}. An Item has geometry, but doesn't render anything. A transparent Rectangle probably also doesn't render, but it's still (at least slightly) more resource-intensive and makes you look like you don't know what you're doing.
Use Loader, StackView and visible liberally to disable stuff that isn't currently relevant. If unloading causes trouble with lost state, you may be carrying too much state on the QML side.
For another perspective and more details, RenderDoc (or another frame debugger if you have one) is a nice tool as well.
Also don't use Rectangle { color: "transparent" }, use Item {}. An Item has geometry, but doesn't render anything. A transparent Rectangle probably also doesn't render, but it's still (at least slightly) more resource-intensive and makes you look like you don't know what you're doing.
Use Loader, StackView and visible liberally to disable stuff that isn't currently relevant. If unloading causes trouble with lost state, you may be carrying too much state on the QML side.