Yeah I believe the extends are off for US/EU versions but no 2nd loop aka violent round if memory serves right. So in that sense it is balanced around 1 loop, not violent round.
JPN aka version JAC on hardest is what I usually play since I like the violent round 2nd loop.JPN default has 1 credit 2lifes, extra life first at 500000, every 1,000,000 after. Those extends are definitely balanced around the 2nd loop imo. I think changing the US version to extra lives and having it loop is fair tbh.
From my experience the AI is a little harder on US/Eu along with food being different foods that heal less vs jpn.
But yeah once bosses get below half health they get up a lot faster. Julius is the fastest at 3-4 frames making his loop pretty tight. Good thing is if you don't want to learn that timing you can just grab him, squeeze him twice, jump twice in the air and grab again. Pretty easy loop.
One of these days would love to get the real arcade board.