I've been using SanDisk for many years, and I still have working cards that are measured in MB, not GB. (Pretty useless for anything these days, but they still work.)
The speed of the card, if it's a reputable manufacturer (which means Samsung or SanDisk - they're the only companies producing the chips), is what the specs call for, for a U1 or U3 card. (It may be faster, but it will never be slower.) Since 4k video needs a U3 card's speed (and 8k video needs a V60 card's speed), just choose the card that meets the spec of the video you're recording. (But Samsung or SanDisk cards - as the article that B. Diddy linked shows, Huawei doesn't sell SD cards, so a card with their name on it may not even be as large as it claims, let alone as fast as it claims. And even companies that do buy the chips from Samsung or SanDisk and make their own cards may be getting second-rate chips. [That includes well-known brands like Kingston and PNY.])