other than the X12 and Nillkin Go, the other TWS that don't produce "walking thuds" is the Dyplay BQC35. if I'm not mistaken,
@webvan already have a unit but don't like it too much?
it is quite bass heavy that i needed to use EQ at first, but lately i found the perfect eartips for it: reversed KZ starline tips. i use 1 size down to M from my usual tips (L). this hack cuts down the midbass by a lot but retains the subbass rumble, making this one of my favorite substitute for a full size headphones.
i also like that it doesn't have much passive noise blocking, i even think it's a bit less than the Nillkin Go, but with the ANC switched on, music would be more clear than the Nillkin. it certainly excel in Gym environment with loud rumbling background music.
the Nillkin still wins on volume headroom though, as even though the Dyplay have enough volume for me at 60 to 80 percent, the Nillkin can be even louder.
i think the Airsun also has minimal thud, but i need to check them again to be sure. the thing that i don't like about it is the occasional drops of the signal, and the charging case is a bit finicky.. sometimes putting the earpiece inside doesn't charge it, so i have to check it several times when i first put it in the case.
darn it... do i need to have 3 X12?? now you make me want to buy the Ultra too
those marble series look great, especially the green one
the Vooplay looks interesting, but if it's basically the same as the X12 but with a facelift, i much prefer the X12 form factor and size anyway