I love Switchy, I use it a lot, even if I don't understand much about the UTM tags 😅
It's very easy to use.
I can create as many pretty links with my domain (eg. go.mydomain.com) as I want and it works perfectly. I can even create different pretty links to the same URL so I know and use one from my website, one from social media and one in emails, so I always know where my visitors come from. I love that. I use it with 2 domains for now but I can add more domains. I can also create several subdomains per domain to create pretty links.
I warmly recommend Switchly, it's a great alternative to bitly and you can manage your own domains, even modify the URL for the same pretty link.
Oh, and I also use the QR code automatic creation, very useful for creating flyers.