I understand that they had to change thri-kreen for DS4. The original version was far too powerful. But I think they made them too humanoid-looking:
Thri-kreen are intelligent insects, not insect-men. DS1 thri-kreen were Large creatures, and we can’t have that, but I still think we can get away with an actual abdomen:
Thri-kreen are supposed to look alien, not like humans with insectioid features.
As with half-giants, halflings, and dray, it’s up to you which of these your character looks more like. But I think the more insect-like version fits the setting better. Plus it explains why thri-kreen have a bonus to Jump. Look at those legs! They’re made for jumping.