No, Sandaime and Yondaime were not equal in power, actually they were nowhere close to one another. BTW, Jiraiya was Yondaime's Sensei, not Sandaime. Yondaime was known as "The yellow Flash" whereas Sandaime was known as "The Professor", the reason for this is that Yondaime was a true prodigy with tremendous skill. While Sandaime was very skilled, his expertise was in his knowledge of Jutsus rather than his raw potential. It was never specified whether or not he used a variation seal, but my theory on that would be spoiler-ridden, and mostly theoretical, so....

As for the link, Leaf Ninja has a bracket at the top that says what areas of its website has Spoilers and what doesn't, so I wouldn't necessarily view it as a spoiler link.