Yes for sure there is less impact in those regards in rugby because one cannot simply launch at the ball-carrier and must ATTEMPT to either wrap or bind when making any contact with a ball carrier. The key word is ATTEMPT.
On the other hand the shoulder and body placement often are more focused and improved such that the impact is often the same, if not more, yet below the neck barring a serious and almost always costly penalty in rugby.
I think there are many variables in any given case pads and helmet or not, but the end result in either sport is a good, clean tackle with a hard hit is just that.
For example in rugby I’ve been on the receiving end taken to ground hard after fielding a kick that went over my head before, and well, I sure was woozy for a few minutes.
By contrast I had delivered in a match several hard hits in attempts to tackle a much larger yet slower tall dude (I was 5-11 and only about 160 at the time and he must have been at least 6-4 and 200), and I had flipped him over in one of the attempts after grounding him a few times. Of course my mates piled on to try to regain possession every time.
Remember you need not succeed in your wrap to tackle in rugby so long as your arms are in a position to wrap. To many onlookers who did not know the rules unlike the referee, my hits looked much like any given cut by a defensive back on some tight end in gridiron. And yes my hits then were not delivered without my own pain as is the common case in pads.