Most of the models are from various Creator sets from the era (some have step-by-step instructions, some just images in the manuals), although I think some of the ones I cannot identify are probably custom builds.
Here's the ones identified for WordBuilder, using the list from Brickipedia plus some better images and info on some unused models:
Land Units
Buggy

4100-1: Maximum Wheels

Dirtbuggy

4100-1: Maximum Wheels

A red version of the yellow model in the game, for which the parts do exist, but not from any one set.
Snail

4101-1: Wild Collection

With some slight color and shell height variation.
Steamshovel

Unknown. Bucket has 7 teeth like 30394 and 2347 but no matches on the sets that use it. It also looks rounder that those real pieces. It's also not clear how the seemingly plate-built arms would connect to those buckets.
Bulldozer (Dozer)

4096-1: Micro Wheels

Forklift

4100-1: Maximum Wheels

They shifted the white vents and tiles below them up a stud though.
Treebot

4099-1: Robobots

Actually an aquatic bot! Orange parts are replaced with yellow or dark grey.
Defender

4099-1: Robobots

The feet are simplified though, and some of the pieces are replaced with white ones.
Dumptruck

4096-1: Micro Wheels

Gas Station

Not an exact match, but 4100-1: Maximum Wheels has something similar.

Robot Lab

Unknown, but possibly inspired by the control towers in 4023-1 Fun and Adventure (as identified in another answer) and 4098-1: High Flyers.

If you are interested, here's instructions for how I think it would be built (setting aside the questionable scaling).

Guard Tower

Unknown, nothing from that time would have had all of those parts in those colors (and nothing has that yellow turntable top).
Looks like a fairly simple build, here are my instructions for it (you will have to substitute the color on the turntable top piece though).

Repairbot

4099-1: Robobots

Looks like they used dark-grey feet instead though.
Amphibious Units
Frog

4101-1: Wild Collection

Duck

4028-1: World of Bricks ?

Very similar, and other models come from this set, but not exact.
Also appears in 4279-1: Creator Strata Red.
Water Units
Fish

4028-1: World of Bricks

A red version with painted eyes, but otherwise identical.
Also appears in 4279-1: Creator Strata Red.
Tugboat

4028-1: World of Bricks

4414-1: Creator Half Tub Blue

Built a little shorter however.
Freighter (formerly Tanker)

(Larger image not available because the tugboat was reused on the info panel.)
4028-1: World of Bricks

4414-1: Creator Half Tub Blue

Looks like blue plates were used on the bottom.
Speedboat

4505-1: Sea Machines

Marina

Essentially just a wider gas station on stilts.
Monsters
Crab

4101-1: Wild Collection

Water Crab

Same design as Crab, but a different color which does not appear in any set as far as I know.
Scorpion

4101-1: Wild Collection

Alligator

4101-1: Wild Collection

Tyrannosaurus Rex

4507-1: Prehistoric Creatures

Shark

4506-1: Deep Sea Predators

Air Units (Unused/Cut)
Bluebird

4101-1: Wild Collection

Almost the same design, but different colors except for the green feet.
Helicopter (Cargo Copter)

Unknown, but has some similarities to models in 4028-1: World of Bricks which may have inspired it.


For WorldBuilder 2, there are only a few additions:
WorldBuilder 2 additions:
Freezebot

4881-1: Robo Platoon

House

4886-1: Building Bonanza

The main portion anyway.
Windmill

4886-1: Building Bonanza

No instructions for this in the manual beyond the rotating mechanism though...
Nursery

No other known depictions, though implied to be related to the Building Bonanza set.
Garage

No other known depictions, though implied to be related to the Building Bonanza set.
Factory

No other known depictions, though implied to be related to the Building Bonanza set.
Lion

4884-1: Wild Hunters

Thanks to LegoSonicBoy, JappaWakka, and qwr for identifying some I missed.