The checkpoint type is set to "Trained" because Version 3.0 has been finetuned. Version 2.0 and 1.0 were purely done by merging checkpoints though.
The baked in VAE is not in fp16 precision, so trying to load it with --vae-in-16fp will produce black images. If you want to use that feature, I would recommend the modified sdxl vae from https://huggingface.co/madebyollin/sdxl-vae-fp16-fix/tree/main. The decoded images will be different, but the difference should only be minor.
Version 3.0
A finetune on top of a Merge of NoobAI_epsilonPred10 with Noobieaterv20. Softens out the harsh linework of the previous versions, while keeping the more saturated colors and higher amount of detail.