TL: DR, Most people land at the P1S or X1C level.
For Bambu, the A1 mini is the only one that is "smaller" (7" bed size). The A1 Mini and A1 are "bed-slingers" meaning they move the bed in the Y (forward-back), where the X and Z are on the arm (single or double). All of the others for Bambu are a "Core XY" system, where the bed only moves in Z (up/down) and the head moves both X and Y. Core XY are usually considered a better system overall.
The P1P is an open frame, the P1S is closed frame. The X1C adds a color screen, a bit more control over the printing from the screen, and better "fault" detection (for something like spaghetti aka. printing lines in space, or detached parts). The H2 series is an even bigger bed, with both a single (H2S) and dual nozzle (H2D). The P2S is similar to the P1S, but adds some general improvements that Bambu has brought to the rest of the series (color screen, faster nozzle swaps like the H2, etc).
Enclosed vs open comes down to what kinds of plastic you want to print with. ABS/ASA/Nylon/etc all need an enclosed space to work properly. While they sell "printer tents", if you think you are going to be making durable parts, things exposed to temp swings, outdoors, etc, get an enclosed printer.
The H2D (dual nozzle) is great if you are planning on doing a bunch of things that need support material, as it can have two things loaded at the same time meaning much less waste swapping plastics. Otherwise, while nice, it isn't needed.
For loading multiple types of plastic, or printing multi-color easier/quicker, Bambu sells an AMS (automatic material system) that can load/unload various rolls for you to the print head. Helpful for swapping, or if your print may run out of a current roll (it can automatically keep going in an identical plastic). Right now, they have three models. The AMS lite (for the A series), the AMS (1), and the AMS 2. The AMS2 is supposed to be backwards compatible with the A series at some point, but the date kept getting pushed back. The Lite is open air, the AMS1 has dessicant slots, and the 2 has active heating available to dry out filaments if needed.
I left out a couple models (X1E, H2C, laser, etc) that aren't really relevant to someone starting out. If you know you need a specific feature these have, great. Otherwise, they clutter the conversation.