[SRB2 Kart 1.3] OpenGL Build VS. Standard Build & Character Editing

So I've seen that SRB2 Kart has two different batch files, Standard and OpenGL. I strongly feel like Standard uses sprites and OpenGL uses models, but I just want to be sure. I know that an easy way to make sprite characters is kartmaker, but what is an easy way to make models?

Also quick note: Models are completely separate from sprites.
Sprites are required for a character WAD to load, but a model is not and can't be packaged in a WAD/PK3 without needing extra files.