I would just power off your S1 system devices, that’s all of them. Then install the S2 App and create a ‘new’ Sonos system with your S2 only device. That will have an entirely different Household ID which you can use under your existing Sonos account credentials or even use a new Sonos account - it’s a matter for you. In my own case I used the same Sonos account.
The main pitfalls are … You have to install all your music services again to the S2 App and perhaps re-create any Sonos playlists you need etc. Also voice assistants, like Amazon Alexa, or Google can only each be used under one Sonos HH ID at any one time. Otherwise you likely won’t see any other issues.
I’ve never had an issue with my own S1/S2 setup that I still run side-by-side on my network with both Apps on my iOS/Android/PC controller devices.
Obviously once you have the S2 only device ‘up and running’ in the S2 App, you can power ‘on’ all your S1 devices and ne’er the twain shall meet, as they have different Sonos HH ID’s.
If you later decide to move an S1/S2 compatible device from your S1 system over to S2, you will need to factory reset it and then add it to the S2 system using ‘Add Product’ in the S2 App.