Karn put the Sand-Sand Fruit Serum away for the time being. His target among Logia fruits was the Rumble-Rumble Fruit, but he needed to determine whether a Logia Devil Fruit's lineage factor was unique within the genetic chain. If it could not be overwritten, he could only consume one Devil Fruit.
As for the claim that two Devil Fruits could not be eaten together, Karn suspected that eating two would cause the genetic chain to conflict and collapse. Until he solved that problem, he had no intention of eating a second Devil Fruit.
He still knew too little about Devil Fruits and needed more test subjects and supporting data. But with the Rumble-Rumble Fruit's powers alone, if he developed them properly, he would essentially be a true god.
Fortunately, Enel was a poor student. If he studied a little or developed the Rumble-Rumble Fruit further, he would become several levels harder to deal with.
If Enel was only at the level he had been at the start of the story, he would still be easy to handle. Given his arrogance, along with the composite insulating clothing Karn had prepared in advance and his magic, Karn was very confident that he could deal with Enel.
Karn had known since his time at Hogwarts that magic could affect electromagnetism. When magic was strong enough, it could stop electric currents from spreading and create something like an insulating force field-Karn's own magical force field.
Karn had already asked Nico Robin to gather information about Sky Island. Once they found the exact location of the Knock Up Stream, he would set out.
When Nico Robin heard Karn ask her to look into Sky Island and the Knock Up Stream, she immediately guessed that her boss was planning to go to Sky Island. She sent