Well with the sump you are trying to add more volume and lower nutrients to create stability so as long as it helps with one of those things then go for it. Personally I wouldn't want another thing to clean and maintain.
some people will continue to use canister filters as a media reactor to run carbon or gfo
etc... You just don't want to keep the regular media in there like bio rings or whatever else comes in there bc they can build up nitrates.
as far as where it goes I would have it separate from the sump completely unless you will be able to have it configured 1. Sump intake and skimmer section 2. Canister 3. Refugium 4. Return. But I don't know I haven't used them so maybe someone else could help with that.
Good luck with the build!