I’d recommend the Ender 3, I have the Ender 3 Pro v2 I believe, and it’s been very reliable and worked right out the box. I got it on sale at micro center for $100 USD, I’ve heard they go on sale fairly regularly.

Assembly is easy. It doesn’t have auto bed leveling, but the adjustment knobs are easy to use (look up some videos on using a piece of paper and moving the X and Y location of the extruded to level).

It doesn’t have error detection, but I’ve seen some mods online that use an Arduino for this. Even with error detection I don’t think it’s recommended to print unattended due to fire risk.

It comes with a removable flexible textured print surface with heated bed. This texture helps with print adhesion by keeping the part being printed secure while printing. And for fragile parts, you can remove the print surface and bend it to help remove the part after printing is finished. This has worked nearly flawlessly for me, compared to earlier printers where people would use painters tape/glue sticks/etc to help with bed adhesion.

An enclosure is a nice addition, but not really necessary unless you’re doing large prints or really trying to push the boundaries of what you can print. The idea of the enclosure is that it keeps heat in to prevent the part from warping as the extruder moves up along the Z axis. For small parts the heated bed will provide enough heat. You can build one out of plexiglass and 3D printed brackets, or an ikea coffee table (look online for examples).