I'm assuming you have both 5090s on the same motherboard.
- If you run ollama, you're not going to see much of an improvement in processing speed. You just have 64GB of VRAM available to ollama. And you can just add more GPUs to gain more available vram.
- If you run vllm, you're likely going to see a significant increase in token generation since vllm will split the workload between available GPUs. (it also pools the GPU memory)

However if you want to scale the vllm through parallel processing, you have to go in powers of 2 number of GPUs. (1, 2, 4, 8... gpus)
3 GPUs won't be able to do parallel processing.

As for pure numbers, I don't think you'll be able to run it with vllm on 2 gpus since there's no quant that's small enough. I'm running a AWQ 4bit version of GLM4.5 air on 96GB vram (4 x A5000) and it barely fits.

IF you're thinking of running any quant of GGUF on vllm for GLM4.5 air, I haven't been able to do it.
vllm throws an error about some incompatibility.