A modern Ryzen chip's integrated graphics will outperform your old gtx 650.

This is a tall order, if you want a real graphics card inside, but something like This (please don't just pick the exact linked one lol) would be an overall upgrade. There are a lot of "compact" "small form factor" PCs out there that companies have already built around a tiny case.

I also don't know what your budget is, but I assume you aren't looking for just a beefy laptop.

The power supply requirements is pretty easy, PC part picker actually has that info on it, where it will estimate the power consumption of a list of parts.

It sounds like you're kind of trying to get away with reusing parts while also going down in form factor. And like, really down in form factor. It's really not going to work as you expect. As old as your build is, not even your RAM will still work in a modern mobo. It would be better if you just thought of this as a completely new build, tbh.

If you want to keep using an HDD I would just recommend getting an enclosure for it and using it as a removable drive. 3.5" drives don't mix with small form-factor PCs. Honestly, I'd do the same for the SSD as well. Most modern builds use m.2 drives, which are about the size of a stick of RAM and slot directly onto the mobo.

Also, please please please do not ship a PC squeezed into a USPS flat rate box. That shit is going to get broken and you are going to be sad.

This isn't as useful if you game, but I find used 1L PCs like Lenovo Thinkcentres to be excellent non-gaming desktops. You can pick them up used on ebay pretty damn cheap, mine is a few years old and I stuck 32GB of RAM, a 1TB NVME drive, and a 2TB 2.5" platter drive in. Some models you can even cram a video card into, using a PCIE riser.

If you're wanting the challenge of reusing as many of the old parts as possible, you'd probably need to start with looking for a mini motherboard that can take your old CPU. That should help figure out what your case needs to be. I'm like 70% confident that a motherboard has a maximum amount of power it can actually make use of so the max amount of watts that your motherboard can use combined with the case will give you an idea of what wattage and form factor of PSU to look for. Probably going to have to give up on reusing the old GPU if it was for a larger form factor. RAM isn't that expensive to get a few 8Gig sticks to max out any newer board.

But I'd also like to second, Maoo, when they recommended looking for a refurbished office PC. Many years ago I bought a Dell Optiplex 6-something-something (it was a huge chunk of metal) but it was a solid base to make a Franken-PC with. I think it ran me about 150 US after shipping and the only real work I did was dig around for some more RAM and plug in a few more drives I had sitting in a drawer. It did everything I needed it to do and I only recently replaced it with a Franken-PC made from parts that are 15 years old instead of 20.

I dont think you can get such small cases with a gpu, but check out silverstone cases, they've small ones (and cheap!) outside of completely boutique brands

Consider buying a used enterprise SFF PC if you don't need to do long-term upgrades of parts. You can get a Dell, Lenovo, or HP SFF PC on eBay with nearly everything you've listed for about $150. At that price point you'll get:

• A nice form factor with high-quality parts.
• 8th gen Intel or comparable Ryzen.
• 8 G RAM.
• At least one nvme slot, at least two 2.5" bays, and at least one 3.5" bay.
• Low-profile PCIe expansion options, including GPUs.
• Depending on the model, a M.2 slot for a wifi card (it might even be included).

This is an extremely good deal. Getting up to 16 G RAM and a wifi card will probably run you $20 or so.

The main downsides are that you'd need a low-profile GPU and some of the components, like the power supply, will be proprietary and not particularly flexible - upgrading individual components over time probably won't be worth the trouble. You'll want to pick your GPU carefully to make sure it's the right dimensions and it can be used and powered by the single PCIe slot that has enough lanes. But also it's $150 base. By the time you really need or want a new computer it'll probably be 5-10 years later and you can just drop another $150 for a 5-10 years newer SFF PC.

You didn't specify a budget or whether or not you're going to do stuff, but your old GPU isn't worth keeping around anymore. Only good thing about it is the low TDP, but even that is wasted power when the integrated GPU will do better and be more efficient. If you want to play games, even a low profile GTX 1650 will be a massive upgrade, and even your APU alone is enough to run plenty of games these days, hell, the Steam Deck is based around an AMD APU.