If you don't like airstones, a HOB
filter or canister with an upward facing output should provide more than enough surface agitation to oxygenate a reasonably stocked tank most of the time.
As far as the airstone goes, I think a higher output pump on a smaller airstone would only make a more intense stream of bubbles. It would still do what you want it to do. If you find that it's just too much, you can try to slightly crimp that airline such that it reduce the pump output somewhat.