Having achieved a target FPS on a particular system may not reflect the same on another system. All the above-mentioned changed done seem to be fine. You could additionally use profiling tools to see what kind of assets take up most of the memory.
Off the top of my head - Using trim sheets, Occlusion culling, and reducing the number of actors running on tick might help improve performance. I mean, there are so many ways to optimize even I’m not sure of haha!