For having undergone this performance update for about 3 weeks now in my scene, I’d say the following: 1600+ drawcalls is just too high for an average performance rig. I have about 2k meshes in scene, 90%+ of which are instances. Yet they still (partly) generate draw calls. I found that anything of more than about 400 drawcalls starts to have a real negative impact on fluidity (read FPS). With an absoluteFPS of about 80 and 700 drawcalls, my FPS drops to around 25 on an MBP 2019 4GB radeon Pro 5300M. It appears the GPU time is taking the most (despite the fact that it is mostly instances). I couldn’t find an ideal, one-fits-all solution for it. In the end lower-end GPU seem to deal better with clones than instances (up to a certain point). Reducing the number of meshes by merging them (and thus, the number of draw calls) also can help. Free active meshes and freezing meshes and materials also did a little (but not much). In the end, I made a combination (and a balance so to say) of improvements and ended-up gaining 30% to 80% performance depending on the view (what is in the frustrum). I still haven’t finished yet with this task. I need to go through the materials and anything that could affect the inter-frame. It’s a long journey and something which, I have to say, I do not particularly appreciate 
Here’s the link to my recent post:
I will likely give it an update/feedback on my new discoveries (if any) once I will have finished with the process (hopefully soon 
That’s all a simple student like myself can say about it at this moment. Still, I hope this can help you find some clues. GL and courage for your project. Of course, if you have any finding to report, I’d love to hear about it. Meanwhile, have a great day 