It’s alright to expose the Sentry DSN (REACT_APP_SENTRY_API_KEY in my case) and the REACT_APP_STRIPE_PUBLISHABLE_KEY is meant to be safe to be publishable too so should be ok.
[Support Guide] Using environment variables on Netlify correctly
I’ve checked this link above and have followed everything exactly, if anyone knows anything that I might need to also check I would greatly appreciate. I’m trying to avoid using netlify.toml and .env because I would rather not commit either of these files in my repo.