Okay as someone who has done VERY extensive testing on rolling - because one of my primary concerns was the roll-ability which was heads-over-heels over most folding bikes - I've tried everything from rollerblade wheels to expensive Brompton-specific wheels to third-party L-fender wheels and here's what I found:

- Racks are the most stable solutions but adds a fair amount of weight
- the extendable wheel addon is AMAZING for stable rolling (haven't found better) - a must imo
- skate wheels are cheap and better for rolling, but adds quite a bit of weight and contributes to heel strike. There's also smaller, lighter built-in bearing skate wheels but those are 3 or more x expensive. Even more expensive are the Brompton specific ones but they work best.

TL;DR: Get the extendable wheel without hesitation. Then choose between rolling on the rear 2 wheels all the time which makes it easier to steer or get a rack where you'll only need to "lift" the bike when you need to turn sharply.

Personally I hated the L-type rolling, but I guess the third wheel is more for setting down than rolling.