Graphic card on optiplex 7020

The Zotac Short version would work but you need the optional 365W power supply.
ZOTAC GeForce GTX 1060 AMP Edition, ZT-P10600B-10M, 6GB GDDR5
https://www.amazon.com/ZOTAC-ZT-P10600B-10M-Dual-link-IceStorm-Graphics/dp/B01IDCOOLC

https://www.amazon.com/OptiPlex-XE2-T1700-T20-vk45-365-alimentación-hu365em-00-hk465/dp/B016PLIUFY/

There is a guy who made his own adapter.

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

MODDIY also makes an adapter.

https://www.moddiy.com/products/Dell-Inspiron-3650-PSU-Main-Power-24-Pin-to-8-Pin-Adapter-Cable-30cm.html

Mini tower I would recommend specific EVGA 700BR with moddiy adapter.

Model:100-BR-0700-K1
SKU:6346160

https://www.bestbuy.com/site/evga-700w-atx12v-eps12v-80-plus-bronze-power-supply-dc-dc-technology-black/6346160.p?skuId=6346160

Non Dell cards require BIOS Secure boot OFF

https://nvidia.custhelp.com/app/answers/detail/a_id/3156