9020 motherboard is standard µATX form factor (i.e. 9.6 in × 9.6 in (244 mm × 244 mm)).

max video card length is slightly longer than the width of motherboard. 
10.5” card would be too long.  https://www.dell.com/community/Optiplex-Desktops/Dell-OptiPlex-9020-amp-Corsair-AX860-PSU/td-p/7477807

Psu depends on which gpu you choose.

Thanks, if it was speedstep he'd say get the EVGA 700BR

Depends on the card and the 9020 model

MT (Mini Tower)
DT (Desktop)
SFF (Small Form Factor)
USFF (Ultra Small Form Factor)

MFF (Micro Form Factor)

AIO (All in One)

USFF  Micro  AIO  cant take cards due to not having slots.

@DELL-Chris M might have more information

 7VK45 / T1M43    365W D365EM-00 is the optional power supply that supports the Dell 1060 card.

There is even a guy who designed and built his own adapter

https://raphtec.wordpress.com/projects/dell-poweredge-t20-atx-power-supply-adapter/

Dell OEM full height but short PCI-E video cards work 

365w PSU =
7VK45 365w, Huntkey
T1M43 365w, Delta    I prefer Delta over Hunkey YMMV

DVP9W Nvidia GeForce GTX 1050 Ti,  4GB, 75w
36V90 Nvidia GeForce GTX 1060, 3GB, 120w
24K8H Nvidia GeForce GTX 1050,  2GB 75w
8CCF1 Nvidia GeForce GT 1030, 30w
1MPR3 AMD R9-360 2GB, 75w
24K8H Nvidia GTX 1050 2GB, 75w

 

https://www.ebay.com/itm/Dell-Optiplex-XE2-3020-7020-Precision-T1700-365W-Power-Supply-D365EM-00-T1M43/154236312104

T1M43