How do I restore the vanilla map?

This can be done, see this discussion:
https://mods.factorio.com/mod/RibbonMaze/discussion/5c9deea5ef0d7a000dfdb5f5

Space is limited!

The limitations of the maze and how it forces you to rethink your factory design is a big part of the logistics puzzle. As a reward, terraforming let's you make more room to scale up to serious megabase sizes.

However, the "Maze block size" and "Clear start chunks" settings give you more space from the start. The wider corridors with "Maze block size" give more room to build, but also require more effort to defend and biters will tend to spawn more readily. You can build a more traditional base with "Clear start chunks", but it also clears resources. This is a deliberate trade-off, so the more you clear, the further you have to go even for starting resources.

I don't really want to go much further with options that give more space, because it will negate the puzzles and rewards that are fundamental to the mod.

Why are resources so rich? Can I lower them?

Resources are rich to avoid relocating lots of outposts over long distances. The "Resource stretch factor" can stretch out the resources so that you have to travel further for the same resources, but use sparingly: maybe set no higher than 4x.

The maze has a sort of map-compressing, optical illusion effect. Resources seem really regular but they are often much less accessible.

They are also limited in size. In vanilla, every so often you discover a large patch of ore. It'll have a high total amount of ore, because of its size for its distance from spawn, but what's really useful about such a patch is that it can fit large numbers of mining drills, and so support a high throughput. We see a rich patch but what we really have is a big patch. In many cases a large base can run with just one big patch of each resource that is relocated as needed.

That can't happen in Ribbon Maze. All patches are 30x30 and richness just indicates how long before depletion. To expand beyond what mining productivity can get you, you must draw upon multiple patches, then either consolidate them in some way, or build a modular base. How to achieve that when the maze paths are narrow? That's the logistics puzzle Ribbon Maze offers.

Relocating mining outposts could really consume a lot of time at the expense of that puzzle. In one real playthrough, the mid-game copper patches were 1200 and 2000 tiles of rail from the start. The next available copper patch was a further 2000 tiles away -- 4000 from start! By comparison, the extent of a Resource Spawner Overhaul region is just 256 tiles by default.

Building an extra 2000 tiles of rail would be a lot of work for a player just to relocate an outpost, and have what they already had, which is a 30x30 square of the same resource. It'd just be grinding. Gaining a new patch is more interesting. The real secret sauce is that each new patch complicates the overall logistics of moving resources around AND of fitting a bigger factory in the narrow corridors to make use of those resources.

So what I'd encourage players to do, is make the most of the rich patches, and keep taking their base to the next level. If your resources are saturated, you should be figuring out how to expand your factory into the maze.