The A7III is a great camera, still one of the best in the market and will still be good several years after, get that and don't get fixated on upgrading your camera once the 7IV, V or VI get announced, lenses are way more important, and your choice of lens is already a good one, but as Jaded said I'd get the Sigma 24-70, seems to be better build, and those 4mm a lot of times make the difference (the Tamron is still a good lens tho).
As for the iPad Pro, I have a 10.5 in which I do tons of work, I work with models and events and so far I've replaced a lot of my workflow with the iPad, I'd get Affinity Photo and Pixelmator Pro Photo as Photoshop/Lightroom replacements, I am a suscriber of Adobe CC so in my case I use Lightroom for color correction and editing photos in batch, for retouching and until Photoshop iPad get more functions I use Affinity, also iOS 13 has corrected a lot of annoyances inherent to the earlier versions of the iPad. There are some times where I have to use a PC tho, but that kind of work I do it on a powerful desktop at home and I am already 2 years without a laptop because the iPad advantages (size, form factor, even the Apple Pencil and don't understimate what you can do by combining several different apps that would take a lot of time replicating on PC/Mac) outweight my need for a laptop