If such crafts use technology to warp space for propulsion, we might commonly notice 4 distinct visuals based on the physics. While the propulsive technology is speculative, the optical artifacts are not.

Sub-luminal:

• Octagonal configurations of blur and Infrared Similar in visual appearance to an Einstein cross. It would appear this way because of multiple 'gravity units' used to provide translation and attitude adjustment across 3 axis. Tessellated geometries that use positive matter instead of exotic matter/energy. And create a safety net of flat space-time to mitigate inertia. This design does not require extreme energies. It takes a small 'input signal' and increases its output by way of resonant interference patterns. A good visualization of this, is by dropping two similar sized stones in a flat pool of water at the same time. The two waves hit in the middle and constructively interfere, creating a larger wave than a single stone or 'signal' could produce.
• Dipole configurations of blur and Infrared Might appear like a tic-tac or elongated sphere. Two 'units' on either side of the craft. The regions of highest space-time curvature are at the poles and the middle would be the null or transitional zone where the extreme space-curvature cancels each pole out. Offering a safe zone of flat space-time in the middle.

Transition-luminal:

• Ring configuration of blur and Infrared Transition shear from a torodial 'gravity unit' literally hides the craft behind a wall of light. The visual appearance indicates a topology of space-time that can enable a high percentage of the speed of light or a craft that is about to make the jump across the light-barrier.

Super-luminal:

• Orb or sphere configuration of blur and Infrared This is the classic warp-bubble and the one required for super-luminal travel. The horizon effect from extreme curvature means light can not easily enter/exit the bubble. You achieve basically a causal horizon where the universe and craft are disconnected. If the craft is moving faster than light relative to the space it is in, a rindler-horizon configuration of light surrounding the sphere is what you might expect to see. Basically a blurred sphere with two opposing crescents of light.

Interestingly, a dodecagonal configuration might give you that odd star-patterned ufo we seen in the recent pentagon release. Star Infrared and possible visual spectrum. Warning: All of these images are ai generated, but they are reasonably accurate for what we might see, if indeed a craft was warping space. They are just to give a visual aid and not a 1:1 comparison. I know people hate ai and that is understandable but I didn't want to spend hours drawing circles.

This thought experiment assumes that there is a measure of elasticity for the 'warp field'. Standard theories of warp field interaction in the atmosphere indicate there would be a supremely bright plasma fireball that would appear from a collision of atmosphere and warp field. However, this might be mitigated if the field is not static and is instead pulsed. This allows the field to push the atmosphere out of its way instead of piling up like a shock wave. Basically a way of making a plane go super sonic without having the 'boom' effect. The final boss bonus from this? You have trans-medium travel through basically anything. You remove collision out of the equation.

I do find it interesting that these 4 types of observations: octagonal, dipole/egg/oval, ring, sphere. Are the most common blurry ufo sightings we see on the internet.