Best practices for integrating an external landing page?

I am using the Academic/Wowchemy theme and have a website hosted in an S3 bucket. I previously built a “subscribe” page that used an embedded form. I have since started using a ConvertKit landing page and updated my “Subscribe” links to point to it.

However, throughout the internet I have links to https://<website>.com/subscribe. It would be nice if I could make it so that when people went there, they would go to the new CK landing page.

What’s the best way to do this? Are there any drawbacks to just creating a re-direct page? Would it make anything easier if I used a custom domain for my CK page (e.g., https://ck.<website>.com?