Electrum does not download the blockchain to your pc. It downloads it to a central server. It does however send change to your main address. For example you receive .1 bitcoin delivered to a receiving address. On your next send of say .05 it will take that .1 from that address and you will find the change under Main account. Electrum meets only one of your criteria. For me I chose electrum because i am running only 120g ssd. If i was to upgrade I may consider running qt but for now electrum is doing what i need it to.
Just to clarify on this, Electrum offers you the choice of whether you want to make use of a change address or not. I personally do not, but it is enabled by default for those who want it.
@OP: Personally, I fail to understand why you would want to use Qt, it's somewhat annoying to have to let it update the blockchain before you can send out a tx. But if you have the internet speed to not have to wait hours for your blockchain to update, and you don't mind backing up your wallet every 100 txs then it's fine to use. I don't like having to continually update my backups so I don't use Qt anymore.