I have no idea if there might be advantages to matching up cards, but I am sure there are no disadvantages! There is an issue with OGL cards and memory, where the amount of memory available to all of the cards is set by the card with the least available memory. So, if you have a display attached to one card, and that display consumes 20% of the card's memory, then ALL of the cards will result in the same loss of 20% memory. There are plenty of people who can explain why that is far better than I can, and I will leave it to them to do so.
I have heard of some adding a less expensive (but still very capable) GPU for the screen and UI, and fully dedicating the card to the app, leaving the other cards explicitly dedicated to Octane for maximum memory. I am not sure yet how to do that, but it does sound like a reasonable approach to take. If you ask in the Vido Card/GPU forum, you will likely get an answer to that very quickly.
Initially, this box was not intended to by my workstation. That changed when I had issues with the Octane network rendering not seeing the box from my laptop workstation. I went round and round with tech support and several people here in the forums, but could not really get it resolved to my satisfaction. It definitely had something to do with ESET security, but it was an intermittent issue, so I cannot say with certainty that was the only issue. In the end, tech support sent me a note saying that the network rendering function for Octane was not fully supported with Cinema, which I think is just a quick out for them. Their sales materials suggest otherwise, as does the experience of many Cinema users in this forum and elsewhere. Aoktar has stated that support for this is really out of his hands; he just passes along data as prescribed by OTOY. Instead, OTOY said I had to purchase another copy of the C4D plug in and use team render. Well, I decided against that, as I had already spent enough money, and switching to the box, in the end, was the better move for me. However, I currently hold an additional license of Octane Standalone that I am not using

my solution will be to build another workstation, though I may not go whole hog with it like I did this one. I think a fast i7 and a couple of cards would be fine for a workstation, though not for sims...
CaseLabs Mercury S8 / ASUS Z10PE-D8 WS / Crucial 64GB 2133 DDR4 / 2 XEON E5-2687W v3 3.1 GHz / EVGA 1600 P2 / 2 EVGA RTX 2080Ti FTW3 Hybrid/ Cinema 4D
Is it fast? Oh, yeah!