Apple recommends their own Blackmagic.
However, the Razer Core X Chroma and ASUS XG-Station-PRO are very good options at a more reasonable price but please note that these are only enclosures. You will need to purchase the GPU separately. This gives you the ability to put any PCIe card in them so you can choose the card that fits your situation and upgrade later.
You should make sure that both your computer and your enclosure support Thunderbolt 3.
MacOS only officially has support for AMD video cards. Apple Support: eGPU is a good read to prepare yourself.
You can purchase multiple slot enclosures but you are likely to run into bandwidth issues over the Thunderbolt connection.
As suggested by @Romen, you could purchase duplicate enclosure/GPU sets. These could be used separately by different users, or together on one computer (if you have multiple Thunderbolt ports).