300W PSU so no real options for a better video card. I don’t know if Dell uses standard ATX or SFX PSUs in these so upgrade options overall might be limited.
They don’t. With few exceptions, they’ve been pretty much proprietary 12V only designs since 4th gen already. Likewise with HP and Lenovo; if one expects to add or upgrade the GPU, these are NOT the computers to start with.
(Note that I am not staff. I just volunteer to help out on the forums.)
No one talking about the “a/s/l?” description?
This is incorrect. Like a third of Dell’s line is just straight ATX, and while it’s sometimes difficult to tell which, the fact is it doesn’t actually matter. The proprietary power system is solely down to the primary board connector. It’s 10 bucks on Amazon for an adaptor.
Tldr:
-Some Dell desktops use ATX psu’s
-The ones that don’t still conform to the ATX form factor but will require a plug converter for the main connection.
So if it cannot physically mount up, it doesn’t matter? 
This is the back side of a EBT2250. Its PSU doesn’t screw in from the rear, so good luck replacing it with a ATX form factor PSU.
Also good luck plugging in an 6-pin or 8-pin adapter on a motherboard that’s has a 12-pin power port. 
The EBT2250 motherboard looks like this:
(Note that I am not staff. I just volunteer to help out on the forums.)
12 pin adapter is 8 dollars: Amazon.com: COMeap 24 Pin to 12 Pin ATX PSU Main Power Adapter Braided Sleeved Cable for Acer Q87 Q87H3 Q87H3-AM 12-inch(30cm) : Electronics
Yeah, like an adapter designed for an Acer from the LGA1150 era (circa 2013) is really going to work …
If you don’t know, DON’T suggest it.
(Note that I am not staff. I just volunteer to help out on the forums.)
That’s just Amazon SEO gaming. The same cable minus sleeves is widely sold. Here’s one on Newegg: https://www.newegg.com/p/2TP-004R-00N95
This isn’t rocket science. People muck around with these all the time. There’s a huge community. The PSU is just to keep idiots locked in. Everyone else takes their well supported cheap hardware from Dell and then does what they want with it. It’s pretty close to how we used macs in the late 80s/early 90s. Like half of those had Frankensteined upgrades that kept them relevant for a decade after purchase.
The “same” cable, but despite the title, the pics show it has 14 pins. 
Yeah, it’s not rocket science. It’s just an electrical fire or so. Also even if someone is crazy enough to try and plug adapters that don’t fit with wiring that doesn’t match up since the so called “same” adapter has incorrect voltages wired to work a 12VO motherboard, that still doesn’t address the physical difference of the power supply itself.
We stopped buying Dell machines at work a while back due to various issues so I haven’t seen any of the last few generations up close. We are now buying a mix of Lenovo and HP, and between those two (for mid-tower size at least) the HP units have been almost completely standard ATX form factor. Lenovo has been hit or miss on the PSU configuration.
Of course we don’t typically add discrete GPUs to any of these, the lone exception being my main workstation, HP Envy TE01, to which I added an Nvidia GTX 1050 we had lying around so I could have better multi-monitor support.
The best option for adding discrete graphics remains a custom built PC, or if you don’t want to or can’t build it yourself, a pre-built from a manufacturer like MSI or Skytech or whatever.