You do have the option for 12 hour retrieval; 48 hour is the discount restore option. We keep the latest backup in the Standard tier and use GDA for older backups.
Integration is an interesting problem though. With Scaleway's c14 cold storage, I felt the reasonable choices were use their S3 services for more or don't use their S3 oriented archive service at all. Moving everything around to different S3 services for different purposes seems like something I don't want to sign up for.
Then your #2 concern should be "when will I want to access this data I store? How much of it? And how quickly?" because that's where Glacier can cost you a new house or car.
So for backups, stuff you don't need often (AND don't need to restore quickly), it's fine. Not so for most other use-cases.
Then R2 is worse for you than S3 as the entire point of R2 seems to be to do a different tradeoff than S3. You pay more for total storage but less for bandwidth with R2, and vice-versa for S3.