The memory modules are standard laptop SO-DIMM DDR4-3200 for the 13th Gen Intel (though the AMD version launching later this year will support DDR5). The storage slot is a standard M.2.

Do you absolutely need to buy the USB-C cards? Probably not, since the motherboard connections are USB-C. But you're gonna have four gaps on the bottom of your laptop, it won't be easy plugging or removing cables, and as someone else already said, the weight of a cord will put strain on the slot whereas the expansion cards put that strain on the case itself instead of the motherboard.

But they're also only $9 each. The laptop itself is $1000+ and you wanna skimp out on $36 for expansion cards? If that's where you're looking at saving money, I'm seriously gonna suggest you look at other laptops that are much cheaper.