I'm kinda dumb lol...

I've read the specsheet countless times but never took note of the rails being labelled :

The last one on teh right is mine , I still have no idea if its both rails combined go into pcie and if it'll be enough tho... I also heard if I put gpu that can draw 75W from pcie and the pcie only can give 25W/50w it might go boom just like 400w psu would go boom if pc asks for 500w

As for the sticker on your PSU saying 3.3v/5v shall not exceed 60w, it means that the power drawn on those rails from the PSU shall not exceed 60w.

You wouldn't be using your current PSU in addition to another.  The new PSU would take the place of it.

Something I checked on:

You'd have to use something like an EVGA B1 or B2 PSU that sits outside the case.  Speedstep regularly recommends 700w-750w because often PSU's boast more total power, but skimp on the 3.3v/5v rails as compared to Dell PSU's.  It is possible your system takes less power on those rails.  It also looks like you did some research, which is good.

Screengrab above shows RX 580 is 185w.

There are some variables, but the above screengrab shows the average system would draw 324w with the card installed while gaming.

I'm NOT saying to try overloading your current PSU, but a good PSU will simply trip if overloaded.  Sparks won't fly like in Star Trek all the time, it shouldn't fry and it shouldn't go boom.

I didn't see it in your photos.  You'd need a PCI-e x16 extender riser cable for the GPU.  https://www.amazon.com/s?k=pci-e+x16+extender&ref=nb_sb_noss  Link shows a few.

I'm doing one more post because it's too late to edit previous.

https://m.youtube.com/results?search_query=Pci-e+x16+extender 

Im pretty sure he recommended evga 700 BR , saying that both b1 and b2 models only have 120w while br has 150w on those rails...

But now the question is do I even need to care about those rails ? I'm pretty sure any psu off the shelf will do more than 65w on 3.3v/5v ?

Pcie might also pull off the 12v instead... The thing that worries me is that I'll buy a psu that can run this machine but I won't be able to use it on anything else afterwards?

I'll have to buy psu that's eps12v right? Or wrong will atx work ? Searching for psu that goes into my dell optiplex 7010 sff I see atx connectors but then agains this is knockoff psu...

At the end of the day if I can get a psu that will serve me good for any modern build later while also being able to fully power this dell that would be nice too... I'm just worried about that 50w pcie slot later tripping even if I swap for beefier psu ? I found threads where they discuss power limits on pcie and say that if card doesn't have enough power from pcie ( I'm assuming pcie powered only ) It won't pull more it just won't work... So maybe nothing bad will happen if I actually do try linking 2nd psu and using like 25w pcie slot just to be safe? I'll experiment with this later I believe for now I'd like to power everything off the 1 psu without buying something obsolete...

It's B1 or BR and not B2.

"So maybe nothing bad will happen if I actually do try linking 2nd psu and using like 25w pcie slot just to be safe?"

It might not be 100% impossible, but linking 2 PSU's together is not advised.  Or...  A single slot card can't use 2 slots.

May be it's better to save some money for a better PC later?

With your 7010 SFF the way it is, it can power a 75w card.  Outside of specs., YouTubers (actual users) have been powering 75w GPU's with 240w-265w PSU's for years.  So may be you could go with a GTX 1050 ti for now.  As for your i7-3770k, 7010 BIOS doesn't allow for overclock.

Oh no I had no intention of linking PCI-E slots - 50w + 25w

More in the line of thinking - If I use lower powered PCI-E slot it won't tax the original 240w psu as much and the rest of the power I can supply via 8 pin... But the question remains will it stress the system if there's a running card that might expect 75w from PCI-E while that slot is only able to dish out 25w? I'm not afraid about gpu not knowing to take power from 8 pin but I'm afraid when it tries taking from PCI-E first it either booms the whole pc or over time the 25w slot burns out?

Same stuff would happen if I toss out 240w psu and use new better one for everything. It could power the pc but at the PCI-E slot what would happen if gpu tries to pull 75w and the slots are only 25w/50w?

Putting a 75w or 50w card in the 25w slot would not tax the PSU any less.  Could it burn out the 25w slot - not sure.

May be it would be better if you just used the 30w GT 1030?  Make sure it comes with low profile short bracket.

Sry I'm not sure if we understand each other...

If card is placed in pfie slot that only allows 25w then that card taxes psu for 25w only vs taxing it at 50w in other slot ?

Sperate psu handles the 8 pin but overall I am looking for psu to replace the old one too and failing. The supplies I find lack wats in +5vsb and -12v rails ( stock is 4a in 5vsb and 0.5a in -12v , while supplies I found generally have 2.5a 5vsb and 0.3a -12v )

I'd go for this right away and research the sheet out of which psu to buy if only I knew that the PCI-E slot could handle it ...