I'm sure everyone can adjust the size of both their JPG and Raw files. I don't understand this whole conversation!! I record JPG's to one card and Raw's to the other if I have two slots. I record both files to my SD card in EOS R and once again, adjust size of files in the menu to meet my needs. What am I missing?
If I were to sum up this whole conversation, well, the reality is that most cameras write to both cards at the limiting cards write rate. So, by using the UHS II card, you are likely limiting the entire camera to ~180 MB/sec write rate (based on observed write rates to EOS-R with UHS II cards, not theoretical "up to" write rates). That is still really good, but after the buffer in the R5 is filled (and we do not know the size of the buffer), the R5's 12 fps will drop to 3-4 fps. If the buffer is small (I measured my M6 II at 1.85 secs and my 5DIV at 2.3 secs with SD card active), if you want to seemlessly use your cards in sequence, etc, this matters. Or, you turn off the SD card, and then you shoot with one card slot and have write rates that are something north of 800 MB/sec, or if you buy Type B, 2 TB/sec, and you render the SD card "useless" (I think that phrase set some people off, but technically, if you ain't using it
.....but this does not affect most users).
Also, and I do not believe this has been mentioned yet, but I think part of the sticker shock here for those of us that care is that in most previous iterations like the 5DIV, sure, there were two card slots, but the write rate from CF UDMA7 to SD UHS I was fairly close (~110 MB/sec to ~78 MB/sec). Here, we are talking about up to 2 TB/sec to 180 MB/sec, so an order of magnitude lower. Will this still be a great camera even if "limited" to UHS II, but this is a limitation compared to CFE write rates.
Also, sounds like you shoot jpg and RAW in different scenarios. Sounds like you do this for file size. If so, keep doing it (I often shoot this way too). But, if you care about fps, you might want to play with your camera. I've read and observed with my own cameras, RAW +JPG after buffer is full is actually slower than RAW + RAW. For example, on my 5DIV in todays test, RAW + RAW was 2 fps after buffer was filled. RAW + JPG was 1.5 fps.