Yeah it seems pretty clear civilian deaths were coming regardless, whether through sustained aerial assault and ground invasion or two nukes. Which choice was less bad is something we can only speculate about

There were way more civilian deaths from the war continuing than from the use of the atom bombs that helped convince the Japanese government to throw in the towel (aside from the parts of it that stubbornly attempted a failed coup to keep the war going, anyway). The Japanese occupation at the time of the atom bombing stretched from eastern China out to Indonesia and was quite brutal to say the least with many millions of civilians killed.