Yes, you can add multiple 123 forms to the exact same Wix site.
If you want to publish for the first time a 123form on Wix, go to the App Market section of your site and add the 123 Form Builder app.
If you need to publish a second form all you need to do is to search again for our app in the Wix Market. Make sure to click on Add Again and not Open App. The publish method is the same.