Given your new information that sometimes you want to render a video while working on another one, I think Roger's idea of having a second computer doing the render is a good one.
Expanding on that, I suggest that instead of getting an interim GPU, that you buy a gaming laptop with a capable GPU, perhaps an NVIDIA 1660 with 6 GB GPU and with 16GB of motherboard RAM, for example this one:
https://www.microcenter.com/product/611 ... ter---back Put the second license for Resolve Studio that you received with your BMPCC 4K on that laptop. Also have an external 1 TB SSD. If you're traveling at a conference, you can copy your footage to the SSD, edit a project and start it rendering while you go back to another conference meeting. Possibly then upload to YouTube overnight, if the hotel WiFi allows it.
When you eventually buy your "beast", you can use your laptop as a render machine at home. You can use the SSD but you might want to figure out how to setup a server so you can share files without having to copy to external drives, perhaps on your "beast" if that's possible (not sure as I haven't done it myself). In the meantime, using the laptop could better inform your purchasing decision on the "beast".
Here's an offer that may help you decide. Make a sample project, then export the .drp and put that file on a filesharing site like Dropbox or Google Drive along with any stills needed to make your titles and any special LUTs you use. I can try that project out on my desktop (see my signature) below using some footage from my BMPCC 4K at whatever compression you use. I can also try it out on an older laptop I have with has similar specs to the one I suggested (1060 GPU and i7-6700HQ). I can let you know how long each machine takes to render the file.