Ah if you’re just Googling for answers it can be quite easy to end up in random places sometimes! This is a forum for a marketplace site mostly used by sellers of handmade items - so we all need to do a bit of product photography, but we’re not all experts on photography and it varies from quick shots on a phone to using DSLRs with more professional looking backdrops.
But I’ll still answer what I can (and being a bit more general) because it might be helpful to others wondering about cameras too.
I’m not a camera expert and don’t think I have the best photos, but this is what’s most important to me.
Although I have a mirrorless camera, I do most of my product photography on my high end compact camera because it just seems a bit quicker and easier. Although some people might find the photos from their phone are fine, I’ve only got a budget smartphone and the photos from either of my cameras are significantly better (even if I was comparing to my 4MP standard compact from 20 years ago
).
If you’ve already got a decent smartphone then the photos from that may be great, but if you’re like me, it can be a lot cheaper to get a separate compact camera than a phone with a great camera.
For a seller, you probably don’t need anything overly fancy and a compact/good phone with a few of the right settings will get the results you need, like @SashaGarrett suggested, a good photo for online is probably more about getting the lighting/set up right.
The settings I find most useful are a good macro (especially if you’re photographing jewellery or other small things, you need to be able to focus up close) and white balance controls (something my phone is terrible at) so it takes away that blue/yellow/pink tinge you get in certain lighting to show the true colours. I also use the option to select focus area a lot, useful if your item isn’t always in the centre of the shot, and for those that like a blurry background, you’ll be looking for a camera that can do a low aperture (f number) - those sorts of options may require a camera with at least some manual settings, but you can get those on compacts as well as DSLRs.
For professional photography you probably do want DSLR or mirrorless… I haven’t used enough of both to be able to compare, but from what I’ve read the main advantage to mirrorless is that you can get faster shots, which will be important if you’re taking action shots such as for sport or gig photography, but it shouldn’t matter for product photography as your subject isn’t moving. However as you mention video quality, I believe mirrorless is meant to be better for that.
I think the main advantage to full frame vs crop frame is about low lighting (full frame being better for low light), so how important that is depends on what you’re photographing and your settings. If for example you were doing gig photography, it’d be very important that your camera performs well in low light because most of your photos will be taken in a fairly dark setting. If you’re taking product photography, you’re in control of the setting so you can just make sure you have enough light to get a good photo. But it can also affect other things, and then which is best may depend on your preferences, such as is it more important to you that your photos look a bit closer, or that you can get a wide angle shot? Would you prefer to have a slightly smaller/lighter camera, or doesn’t it make a difference.
Looking at cameras can get a bit overwhelming, and they might often shout about features that sound impressive but often aren’t that important to you. Such as megapixels - I often think cameras/phones go really overboard on this these days, making it sound as if you need 40MP+ when really for sharing online, 8MP would be perfectly fine and could be just the same quality. As most cameras/phones would be at least that these days, I wouldn’t really pay attention to megapixels unless your photos are needed for print (which a professional product photographer would need), and then work out what the maximum size print you’re likely to need is and what the equivalent MP is. Once you’ve narrowed your choice down to cameras that meet that, focus on the other features that will make more difference to the quality/ease of use.
Remember, if you’re just taking photos of your products to use in your shop online, you’re probably not going to need the biggest, fanciest camera. If you’re not familiar with what all the camera controls do, a fully manual camera isn’t going to get you great photos without a lot of time learning - it’s more likely to overwhelm you and put you off taking photos. The best camera may not be the best camera for you, make sure you pick one you feel comfortable using rather than than one that confuses you.