Midi controlled LED by USB
I did some time ago something very similar, except not using USB, and on an STM32 (Arduino compatible STM32F103C8T6), but the principle is similar.

Regarding another MIDI test I did on an Arduino, I used the 47 Effects library and for the WS2813 (software-compatible with WS2812B) the FastLed library.

One MIDI port is easy to use (supported by 47 Effects), which uses the single UART of the Arduino UNO.

You have to write a small program to convert the MIDI notes to WS2812 LED data, which is not much more than filling in a structure. Mapping 61 or 88 notes to 30, 60 or 144 LED notes is not so easy, just clip the notes, or use some mapping factor.

You cannot use the Arduino for powering the LED strip, use a separate adapter for that. Only the line signal comes from the Arduino, and connect GNDs together.

The Arduino should be fast enough to both read MIDI, translate it to LED data (unless you make some very time consuming algorithm) and send the data.