The CW5200 has more cooling capacity than the CW5000 (that’s the difference). I’d think (not an expert here) that especially if you think you might upgrade to a larger laser later, the extra for a CW5200 over a CW5000 would make sense. When asking for purchase suggestions, it’s a good idea to Display your national flag with your user name Since you linked to a UK supply, I assume you are in the UK — otherwise I’d be suggesting to also look at the Lightobject chillers.
For cutting plywood, I’d suggest searching the site here for experience cutting plywood. Different batches tend to cut differently, knots in inner plys can make for incomplete cuts, and some plywood has metal in the glue (on purpose!). In the US, there is now a specialty plywood supplier that makes plywood expressly for laser cutting, with no knots in any ply and glue that’s appropriate for laser cutting. If you are going to make a business out of this, it might be worth looking for this in the UK.