You can find in the market different solutions, egpu devices that already include a GPU card or you can buy your egpu device and choose your preferred card.
Probably the most used and sold is Razer Core X (egpu only) because its power unit can handle almost all cards and usually you can find It at reasonable cost.
Instead Apple via store in the past proposed other devices (with GPU included), pro of this solutions is support from Apple and also these devices were considered really silent. But if I remember correctly these are now out of stock/end of life and based on old gpus.
Among the recent products there is the Akitio Node Titan (available just as egpu only or also with GPU included) but currently there are few reviews online.
I'm also considering to buy an egpu for my Mini 2018 but currently I'm thinking to Razer Core X, have a lot of doubts about the card. I have no real need for an egpu, probably the only app that could benefit is X-Plane and I have only 1080p displays, so I was thinking to Radeon rx 5500 XT 8g but I'm not sure if this cards is really officially supported by Apple (in their site they mention Navi architecture but the only models explicitely named are the 5700 and 5700 XT).
Anyway for other info on egpu world and experiences from users I suggest to give a look ti egpu.io site