@akos_szablya, macOS will be more suitable for large libraries when we release native support for the M1/M1x chips.
This work is in progress. For now, I don’t think the bigger Macbook Pro will make much of a difference, as the limitation is less about the speed of the machine and more about how Roon runs on a mac.
With a huge library (yours is in the 99.94th percentile among Roon users), you should really use an always-on, dedicated core with lots of RAM, ideally running Roon OS, but Windows would be OK too.
On a laptop, Roon will take a long time to start up, and consume a lot of RAM. It will diminish the overall experience of using the laptop for other things. For extreme configurations like this, Roon was really meant to run on dedicated hardware.