Nole and Nadal would do good in 90s. Nole would still win HC titles and had great shot at Rg and none at Wimb. Nadal would own clay badly and Mugray would be fine too. They are far superior on physical level, fast court or not they would adapt and rack up few slams.
So, Nole, Nadal and Murray would adapt in the 90s, but Sampras and Agassi would not adapt in the 2000s. That's either underestimating the two or not being objective at all.
First of all, in the case of each switch, it is mandatory to believe that the players' game will form differently. So, you wouldn't be having the same Sampras or Agassi that adapted for the 90s courts, you would have a different game from both of them and given their enormous talent, they would win Slams, but the era would consist of a Big 6 rather than a Big 4. Nole, Murray and Nadal would also have a different less physical game in the 90s adapted for a faster HC, Carpet and grass, and a slower clay. Their talent would allow them to be big in the 90s as well.