The question might be: which Macbook might your prospective usershave? For that reason I'd go with something low spec, maybe even a refurb from https://www.apple.com/shop/refurbished/mac .
(To translate back to the Windows world - if you were making an app for Windows you'd want to make sure it works on the cheap stuff at Best Buy, not just a high-end Dell XPS with 16G RAM, because most users have a cheap thing).
If your app works on a lower-end machine it should work on a higher-end one. You can run and test an Intel build on an ARM machine, you can't run and test an ARM build on an Intel machine.
In the event that your app only runs on high-end Macs - for example if it's an opportunistic port but you don't have the resources to work on Mac performance - you'll probably want to think about how to message that, before you reach the point of people downloading it and becoming loudly disappointed.
(To translate back to the Windows world - if you were making an app for Windows you'd want to make sure it works on the cheap stuff at Best Buy, not just a high-end Dell XPS with 16G RAM, because most users have a cheap thing).
If your app works on a lower-end machine it should work on a higher-end one. You can run and test an Intel build on an ARM machine, you can't run and test an ARM build on an Intel machine.
In the event that your app only runs on high-end Macs - for example if it's an opportunistic port but you don't have the resources to work on Mac performance - you'll probably want to think about how to message that, before you reach the point of people downloading it and becoming loudly disappointed.