Big wing, more than needed at usual landing weights in the -200, giving significant ground effect, especially if you’re a few knots over approaching the flare.
My experience has been that the best landings (comfort wise) are when you touch down with a small RoD, 100-200fpm, taking up the slack in the oleos before the speed brakes deploy and do it forcefully.
It is very easy to over-flare the 777, like others have said it is just a small check and hold, unless you’re going down fast at slow speed. Too pronounced a rotation gives a short fly-by followed by a bit of a thump as by then the speed has decayed.
The -300 with much higher landing weights on a wing that is not that much larger than the -200 means significantly higher speeds, so a higher RoD into the flare. The longer fuselage plays a part but I don’t really change my technique for the -300 as it’s too subtle for a coarse pilot like me...