I wrote a tweet thread a while ago with my own opinion on RW vs Remix, here’s what I said:
As you know, I’m a huge proponent of frameworks learning from each other and I think both have a ton to offer. I love Remix’s emphasis on web standard APIs and shipping less JS whenever possible. The conventions they add on top are very intuitive.
Biggest differences to me are the degree to which they emphasize the part of the stack that talks to the database and how the auth is managed. Remix says it’s the View and Controller in MVC, but leaves the Model up to you. You can bring in Prisma easily to handle the M but it’s not included by default.
RW, on the other hand, does the opposite. It includes Prisma by default and you can rip it out if you want. Redwood also has built in authentication and a ton of third party provider integrations.
I have no doubt Remix will be building out similar features but as of now I think there’s mostly just community packages and one section in the docs about auth. And then of course there’s the question of do you want to use GraphQL or not which is its own debate unto itself.
This is already a little out of date because a few weeks after I wrote this Remix released Remix Stacks which are Remix starters that are much more similar to Redwood apps than what they offered before they had these stacks.
In terms of having a Remix side, you could use Remix today to make GraphQL calls to a Redwood API much like I do in my Next and SvelteKit examples.
Hope that’s helpful 
.