HDMI is correct for cameras, game consoles, computers, mixers, and anything with an HDMI output. SDI is for professional broadcast cameras, routing switchers, and broadcast-grade equipment. If you are not sure you need SDI, you probably need HDMI.
Loop-through passes the same signal to a local monitor while capturing. You need it if your HDMI source has only one output, because without it you cannot both capture and display on a local screen simultaneously.
The Gen 2 range has no loop-through. The Plus range has loop-through. If you are using a camera with a single HDMI output and want to monitor on a screen, buy Plus.
Gen 2 and standard Plus models capture up to 1080p60. If your source is 4K (PS5, high-end camera, 4K computer output), you need the 4K Plus or 4K Pro models.
The 4K Pro uses the latest enhanced FPGA processing engine for superior colour accuracy and is the better choice for critical professional applications including medical imaging.
HDMI Gen 2: 1080p60, no loop-through, no audio jacks. Streaming, conferencing, anything where you do not need a monitor connected simultaneously.
HDMI Plus: 1080p60 with zero-latency loop-through and 3.5mm audio. Gaming, presentations, streaming where you need a local display.
HDMI 4K Plus: 4K60 with loop-through and audio. 4K game capture, professional 4K streaming.
HDMI 4K Pro: 4K60 with enhanced FPGA, loop-through and audio. Best available. Medical imaging, critical colour work, premium production.
AIO: 1080p60 from HDMI, SDI, DVI, VGA, or Component. One device for multiple input types.