If you are sensible with what you download, you should in theory be okay to not install the updates automatically. If there’s news that a new worm is doing the rounds it would be wise to update but given your internet situation your current method should be okay.
Remember Microsoft release updates on a schedule, the 2nd Tuesday each month if I am correct.
If you have multiple W10 computers in your home there’s an option somewhere to download the updates to one and have it share them out - I’ve never been able to get this to work myself though.