The generation the Optiplex 7050 is in isn't the best for big gaming upgrades.  From the spec sheet:  Supports optional discrete graphics Tower/Small Form Factor: AMD Radeon™ R5 430 1GB/2GB, AMD Radeon™ R7 450 4GB

Though the GTX 1660 would likely fit in the tower (too fat for an SFF, needs to be LP (low profile)), the 7050 comes with a 240w PSU (tower) or 180w PSU (SFF) which can't power a 120w GPU which requires an additional 1x8-pin connection.  Other than what's listed, it's hard to recommend any GPU to go with 180w PSU.  I don't think super low watt GPU is what you're looking for.

A couple of things to consider - a little older or newer; may depend upon budget.  Older meaning a 9020 or XE2 which are bigger towers, introduced around 2014 or newer.  The full-size towers can take full-size PSU upgrades, which would be necessary for the GTX 1660.  A full-size PSU would have to sit outside the 7050 tower.

Then there's the generation newer than the 7050, XX80's and XX90's.  The 7080 and 7090 both have available 500w PSU's.  Spec sheets can be Googled.  Optiplex 7080 Spec Sheet  Optiplex 7090 Spec Sheet 

If there's a higher watt PSU crossover for the 7050, redxps630 will know it before I will and might chime in, but it would have to be the tower for the GTX 1660 being looked at.

P.S.  ASUS GeForce GTX 1660 Overclocked 6GB Phoenix Fan Edition needs at least a 450w PSU.

As I mentioned a previous generation of the Optiplex, whichever Optiplex you consider, we can check the possibility of bottleneck between GPU and CPU.

brad is correct that PH-GTX1660-O6G is a full height card and would not fit a SFF case.

Low profile cards are limited to a maximum height of 2.536 inches.

to support i7-7700 in 7050 and gtx 1660 you would need a 360+w psu.

Load Wattage:316 W
Recommended PSU Wattage:366 W

even if you do not use hdd and odd, the recommended psu is still 325w.

psu can be upgraded to a higher power Dell proprietary psu (360w, 460w, or 500w).   because 1660 requires an 8 pin PCIe connector, Dell psu needs to have a 6 pin (which is effectively 8 pin).

for example, Dell 360w psu PCFT5 Chicony or 2VD0G 360w Liteon

GENUINE Dell XPS 8940 Desktop Power Supply PSU H360EBM-00 PCFT5 360W 80+ Bronze | eBay

re: cpu and gpu match

i7-7700 w 1660 is good for 1080p gaming overall, not very good for 1440p, and not good for 4k.

GTX 1660 benchmark with i7-7700 1080p, 1440p, Ultrawide, 4K benchmarks at Ultra Quality - GPUCheck United States / USA

The only thing I don't agree on is PSU.  I don't think PSU should be stretched to the max or close to it.  Better to have some power left over.  With redxps630 knowing more about PSU's than I do, either one could be right.

7060 SFF case is also low profile and would not support full profile gpu such as  PH-GTX1660-O6G.

if you can here is a link of the gpu im thinking of putting in it, would it fit being single fan?

https://www.amazon.com.au/gp/product/B07PHWBHHX/ref=ox_sc_act_title_2?smid=A1F1LZOG5L7SNX&psc=1

thanks for the reply, im thinking of getting the 7060 now with i5 8th gen, if i got it (sff) and upgraded the psu to a genuine dell 500watt psu would it work with the graphics card?

thanks  

Here's an example of a card that can be LP.  It has both brackets, one for towers and small one for DT's and SFF's.  https://www.bestbuy.com/site/pny-geforce-gt1030-2gb-pci-e-3-0-graphics-card-black/5901353.p?skuId=5901353&ref=212&loc=1&extStoreId=27&ref=212&loc=1&gclid=CjwKCAiAwKyNBhBfEiwA_mrUMgvANBphwxul1XPbuz3Qgh3kZ_9elc8H9ybaXKqnfA_dVDC8c4XRHRoCqZsQAvD_BwE&gclsrc=aw.ds