Never measured, so I do not know. But I know that the right side of the space bar on my Pirixx full-size keyboard ends at a different key position than on a 100% board. Tis true the other clusters are farther apart, as groups, on the Pirixx than on the Keychron. Typing on the Keycron feels a little more compressed to my hands initially. I still make a few typing errors, I will improve.
Different profile keycaps can make things feel different - think of keycaps as equal-base pyramids with the top point cut off. A taller pyramid will have a smaller top surface and more apparent space between its neighbors, while a shorter one will have a bigger top surface but less apparent space between its neighbors. This can change how the keyboard feels to your fingertips, but the key bases themselves are in exactly the same positions.
This is what you may be feeling between the Keychron (which comes with their own unique OSA-profile keycaps) and your other keyboard, which likely is using Cherry or OEM-profile keycaps. They'll feel different despite the fact that the keys themselves are spaced exactly the same at their bases.
As for 100% -- both keyboards use a 100% layout. Not sure what to tell you there. I'd include a picture of a 100% layout, but it would be the
same as the picture I posted above.
The Keychron C2 and the vast majority of other 100% layouts use a 6.25u spacebar, giving you three 1.25u modifiers to the left of the spacebar and four 1.25u modifiers to the right of the spacebar. A few will use a longer 7u spacebar, giving you 3 modifiers on each side (1.5u - 1u - 1.5u each). Perhaps that's what you're seeing different between the two?? But that doesn't make one a 100% layout and the other a not-a-100% layout. A few keyboards will use spacebars
shorter than 6.25u to cram in additional bottom row modifiers (looking at you, Apple!) on their 100% layouts.
The so-called 96% layout (aka, 1800 layout) does away with the center navigational cluster, moving the numpad immediately next to the alphas, usually replaces the 2u numpad Zero key with a 1u Zero key, and uses a shorter right Shift key to make room for the arrow cluster. See the Keychron
V5 for an example of a traditional 1800/96% layout.
A 98% layout is a somewhat newer variant that adds a single column of navigation keys between the alphas and the numpad (as compared to the 3-column navigation cluster on a 100% keyboard or an 80% TKL), which also often makes room to return to a wide 2u numpad Zero key.
The bottom (spacebar) row configuration can be variable on these as well, and also doesn't change the layout type designation. 1800's and 98% often use three 1.25u modifiers to the left of the spacebar and three 1u modifiers to the right of the spacebar (i.e., Keychron
Q5), but some will use two 1.25u or two 1.5u modifiers instead, as does the Neo98 and the (somewhat inappropriately named) Athena 1800 (since it's really a 98% layout and not acutally an 1800 layout).
But the 96% and 98% layouts are easily differentiated on sight from a "100% layout."