I always torqued those strut-top nuts down by shoving whatever two hand tools I could get to work together, at whatever angle would make them work. Sometimes it gets agonizing like 3 degrees of movement... never bought myself any of those fancy window sockets for the job because every vehicle and even every replacement shock/strut seems to use differently sized hardware. Not worth buying them all if you're not a shop working on cars daily for a living.
The only time I would ever use an impact on them is removing an old set I'm going to throw away because it doesn't matter if they get damaged.