Building on the earlier suggestion, I actually went through a bit of a trial and error phase when I first picked up my FX30. Tbh I was pretty stressed about the storage costs at first because these modern codecs are huge.

• I originally bought the fastest, most expensive card I could find, but it was so pricey I could only afford one tiny 80GB card. I spent more time offloading footage than actually shooting.
• After some DIY testing, I realized that for my documentary work, I needed capacity more than raw speed for about 90% of what I do.
• I switched my strategy and found that my current setup handles 4K 10-bit stuff perfectly fine without needing the absolute top-tier gear. I have been super satisfied using ProGrade Digital SDXC UHS-II V60 Gold for my general day-to-day shooting. It works well and I havent had any issues with overheating or buffering. For the times I really want to push the slow-mo at 120fps, I usually pop in the Kingston Canvas React Plus V90 which is a bit faster but still way more affordable than those Type A cards. No complaints so far, it just works.

The FX30 has dual card slots - one for CFexpress Type A/SD and one for SD only. For the best performance (especially with 4K 120fps or 4K 60fps 10-bit), I'd recommend Sony's CFexpress Type A cards. They're expensive but bulletproof - I've never had a corrupted file. If budget is a concern, high-quality V90 SD cards will handle most shooting scenarios. I use a mix depending on the project requirements.

Same boat, watching this

CFexpress Type A card: Lexar CFexpress Type A Gold Series.

UHS- II V90 card: SanDisk Extreme Pro UHS-II V90.

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Are you planning to shoot a lot of slow-motion? If so, the absolute fastest cards are essential to avoid dropped frames. I'd highly recommend the Angelbird AV Pro CFexpress Type A cards. They're specifically designed for high-bitrate video and offer exceptional performance, even with demanding codecs and frame rates. The Delkin Devices POWER CFexpress Type A cards are another great option in this category.