The huge factor to a great FG score is not only 3 vs 5 ball, but if you set the switches to the highest difficulty. I would think 5 balls & easy settings should get you to 1M+ scores more often. But FG is all about taking a beating & proving your worth, so I'm not a fan of making it any easier.
Mine is set for 3 Ball. I have all the switches set to the most conservative difficult settings, no circle insert carryovers from ball to ball. No rewards for reaching default replay scores at 600K & 1.1M. And only one Extra Ball may be earned per game.
I was able to get just over 2.5M with those difficult settings about 2 years ago, and let me tell you, it was the most intense stressful game I've ever played. Getting 5x lit, ripping both lit spinners for huge points (with 15sec bonus running) & getting the ball back under control. Rinse, repeat. Crazy shit. I haven't even sniffed 1M in the last year.
I would argue that FG has absolutely nothing to do with luck. It requires the most skill of any game to reach high scores, especially when there are no carryovers from ball to ball. You have to nudge. You have to make your shots, then get the ball back under control for the next shot. Draining is starting from scratch & tearing your hair out. If you're just slapping away, the center pops & slings are going to end your ball in less than 20 seconds.
Non-pinheads come over & won't even touch it, they say it's just too hard. That's fine with me. I think it's the best pin ever made & it's never leaving my collection.