The RS trim package is an aesthetic upgrade more than anything else. Traditionally in the world of Chevrolet, RS stands for "Rally Sport" which signifies some major performance upgrade against the next closest trim level, but that isn't the case for this generation of Blazers. The only difference for the 2021 model years was that the AWD system for the RS and Premier level trims is slightly more advanced than those for the L's and LT's. If you're like me and have a LT model with the V6, AWD, and towing package, there's really no difference between our LT's and the RS aside from the hard/soft trim finishes.
You should be okay to proceed with the Magnaflow exhaust and Eibach sport springs. Are you doing a full exhaust system replacement or just a "cat-back"?
Also, just remember that if you should need to take the car to the dealer for any manufacturer warranty claims related to your exhaust or suspension systems, they will probably be voided from doing these mods. If that's not a concern, have at it and be sure to share how the results come out!