I'm interested in this as well. I rarely see macbooks on tour anymore - apart from simple QLab setups in theaters. In the scenarios I hear about them, it is usually problematic (dongles not working, overheating etc). We still have 2015 models running QLab/Keynote, and haven't had any compelling reasons hardware-wise to upgrade them apart from wear & tear/physical damage. USB-C has been a huge hit to reliability on the road. Going forward, we're limiting the builds to rackmount mac minis for QLab/Keynote, and Resolume/MadMapper will be running on PCs instead.
The new Mac Pros are also too little too late, and at a price point where they compete with dedicated media servers/solutions - I'm not certain they bring anything to the table. It does have the rackmount capabilities, but otoh you can build a rackmount crazy dual GPU powerhouse for the MP entry level price (which has 4GHz 8c/16t rx580/32G ram). My current home computer is better specced than that for half the price. Including a monitor. With a stand.
And to clarify, I'm not a disgruntled Apple customer - I just don't see the financial sense or prevalence in Apple equipment for this line of work any more.
Couple of things comes to mind. First it seems like you're always creating the full resolution image. In the case of the low-res selection, you only see the lower res one, but in the comp you also create the full-res one anyways. This is one of the major differences between QC and Vuo. In QC you wouldn't have created the one that wasn't selected, as it pulls the values to the output. In Vuo however, it pushes all calculations to the conclusion from the inputs enabling background calculations, but at the price of having to be a bit more careful about the values and blocking events.
I also wonder how you deal with the wrap-mode in QC? I haven't used this (vuo) node myself, but if I understand it correctly, it in this instance would check 4 4k frames/textures at every frame cycle. That is a pretty hefty operation - especially for older/mac hw. I would try removing those nodes to check performance.