OP there is a difference
This shows it in a clearer way – https://www.apple.com/uk/shop/buy-mac/imac
Effectively there’s a base model with one less GPU core, and no gigabit ethernet (I think they are the only differences, maybe slightly less cooling too). It still has the same hardware accelerators so for most normal people (eg not looking to demand GPU too much) they won’t notice the difference. If you’re (properly) video editing then get the one with 8gpu.
Plenty of info and comparisons on YouTube…
Good call on the M1. Beautiful screen and blazing fast chipset. Dead silent, etc. It’s basically a 24″ iPad. Everything just works, immediately and with 0 fuss. Unlike intel.
Tip When you get it it comes at a lower effective resolution than 4.5k, you need to go into graphics settings and change it to ‘more space’ if you want more screen real estate.