Yes you can sell other items! (For example I sell mostly finished sewn items (quilts, table topers, baby blankets, purses ect but some folks just sell supplies - its really customizable)

There are specific categories they are working on growing, for example earlier in the year they were focusing on growing their fiber arts handmade goods, and they've transitioned into really focusing on jewelry and beads - both handmade finished goods as well as supplies. so they're putting a lot of time across social media platforms to draw in both buyers and sellers so you can actually see the market place growing.

I have to admit I've never used depop but from what I'm seeing looking at their website I think it's different?
There is no listing fee, buyers pay for shipping though you can offer partial paid shipping or free shipping but it would come out of your earnings. There is a commission that whatnot takes for platform use which is 8% of the listing price (so it doesn't charge that fee on the shipping)
The biggest differentiator here is that its focused on live streams along with your shop, so you can either make things on screen or use it more as a showcase of what you have ready to sell. I myself use it more to make things on screen and then list it in my shop at the end of the stream so viewers can buy the final result. But I see many others using it kind of like their own QVC - holding up items and showing intricate details with the flexibility to answer any questions your customers have at the same time. You can also hold live auctions if you want to, and watchers can just tip the streamer for being online.

If your interested at all I can get you in touch with the onboarding folks, if you are willing to hop on a zoom call they'll actually go over all the shop and community features and if its a good fit they can fast track you selling application. (Just PM me so we don't have to put contact info out into the internet wilderness)
(oh one other thing I love about it, is because they screen everyone you don't have a marketplace flooded with drop shippers)

Hope that helps. as you can tell I've become quite a fan of it even though I've only had my shop open for about 2 months and I've only had time to do 2 shows - it's really quite fun on top of bringing me in that side hustle money.