The only rough sea day we experienced was after we passed the Rock of Gibraltar.
They said the seas had 10-15 foot swells that day, but I think they were smaller than that.
This was our first crossing and we had no problems with the motion.
As for the time changes, we were headed West, so we kept gaining an extra hour, instead of losing one. I know of at least one cruise vlogger who doesn't reccomend Eastbound transit sailings because of the lost hours. You'll know soon enough how your body handles it.
You'll have a great cruise....the food is wonderful, and the crew will be thrilled that they are done with the 4-5 day sailings they've been dealing with for a while.