Ok let's break this down into multiple things we want to optimize for:
- Flexible morphology - squeeze into any size space
- Manipulator size range
- In-built tools
- Sensor sensitivity
- Sensor variety
- Processing power to make sense of the inputs
Assumptions I'm making:
- Terrestrial Earth
- In the size range of humans (as opposed to ant or blue whale sized)
The fastest mode of travel outside the ocean is flight, but making something flight capable would be really hard on everything else so I'm assuming "running fast" is the speed target.
Flexible morphology is antithetical to running quickly since you need strong bones to push off and also absorb impacts.
The best trade-off in that respect is a feline body plan, fast moving but also able to squeeze into small spaces.
So a cat-like basic body plan to start with plus slightly bendier bones.
Opposable thumbs are a must, and the addition of sharp and blunt instruments would be great too. However the more complicated the manipulator the more delicate it becomes, so ideally limbs would end in something sturdy, like hooves, with the delicate tool-enhanced manipulators able to be retracted for movement.
Two manipulator limbs is good for me, fewer complications the better since we need to save as many neurons as possible for the Perception section.
For biological machines strength is just a function of muscle cross-section, so we can't really optimize for strength beyond the maximum musculature possible on the number of limbs. We could maybe use more advanced actuators instead of muscles but that's an engineering implementation concern and doesn't affect the overall design of the creature.
So now we have a cat-like body plan, with hooves for moving around on and retractable "fingers"/"thumbs" with a variety of built-in tools for dexterity when manipulating things is required.
Humans can sense Light, Sound, Temperature, Texture, certain chemicals, electrical currents. Some animals have sensitivity to electric and magnetic fields as well, so that can be added to the list of known biological sensors.
So sensitive versions of Eyes, Ears, Nose, Taste receptors (maybe as a manipulator tool like butterflies have on their feet so that you can test chemical properties safely), touch sensors and magnetic/electric biological sensors.
The risk with highly sensitive sensors is that they can easily be overloaded and cause harm, so the ears/nose are closable, eyes have eyelids and maybe can retract into the skull a little for safety, and the electric/magnetic ones have biological circuit breakers to avoid causing damage in the event of sudden, strong fields.
So now we have a cat-like body plan, with slightly bendier bones. It has hooves for moving around on and retractable "fingers"/"thumbs" with a variety of built-in tools for dexterity when manipulating things is required. The creature has huge eyes, ears and large nostrils. It also has a long snout with plenty of space for nasal sensory machinery. It has a huge cranium, since there are a lot of sensory neurons and they have to go somewhere for processing. It has regular face whiskers but all over its body it also has other whiskers periodically to sense all kinds of air currents.
Now finally does this body look like a weird but recognizable existing animal? Or is it exaggerated until it becomes bizarre and unsettling? That depends on if this body has to hunt/forage for food and avoid predators or are we part of a post-scarcity society where such needs are satisfied by default? If it's the latter then the body can essentially just be a giant brain and sensory/tool apparatus on legs. It likely has some photosynthetic capability to reduce the energy requirement but running all that computing will likely be impossible without some kind of sustenance. If it needs to hunt/forage it has a mouth with lots of kinds of teeth and digestive tract, if not it has a simple port for input of optimized nutrient slurry / electrical power. Or an inbuilt RF receiver for wireless power, whichever is the easiest to obtain.
And so that's the design I'd go with, kinda weird looking but effective at all the things we want it to be effective at.