100% agree with adding a coating agent after printing, but if you’re looking to minimize small holes and fissures, consistent line width is super important. High speeds can make thinner lines than when it slows down at starts/stops and corners.
Printing PETG slower than PLA is already a common recommendation, but unless your printer supports input shaping and linear (or pressure) advance, I’d go as slow as you can bear. As a perk, if 245 is the optimal temp for your usual speed, going slower will make 240 work better.