As far as rules, I did mine for what would work out and look good for me. I also made sure that the side faucet knob did not interfere with any of the other items. Here's a pic of left to right--Soap, faucet, airswitch, and hot/chilled water faucet: It has worked out great!!

I have the Waterstone Traditional PLP at my main sink (LOVE IT!) along with the hot/cold faucet and a a soap dispenser. I have a 36" sink and it isn't crowded at all. Plenty of room to add an air switch and another dispenser for lotion. I also bought an air switch for the garbage disposal but ended up not using it and stayed with the wall switch. My reason for doing that had to do with safety after watching my daughter playing with every button and knob when we were in at a store. It looked like something fun for her to play with. The wall switch doesn't give her temptation and it far enough away that she'd really have to work at it to get her hand down the disposal and flip the switch at the same time. I agree the switch is beautiful. At the island prep sink I added a switch under the counter for the disposal. The kids think that is pretty cool and showed it off to friends when the kitchen was first done, but now, out of sight out of mind. They don't touch it. I love my soap dispenser (the NeverMT is a must!) and use it a lot. I still have a bottle of dish soap on the counter and use it a lot too. It just depends on what I'm doing but I love having both. I tend to grab the bottle of soap (I keep it in a pretty olive oil dispenser) when I want soap in a specific place, like a pot or pan that I'm washing. I tend to use the built in dispenser when my hands are dirty or I want to pump some soap on my sponge. There are a lot of pretty dispensers out there if you want to keep soap on the counter. We don't use a separate hand soap and only use dish soap in the kitchen. I used to have a lotion dispenser in my previous kitchen and got so tired of people trying to wash dishes or their hands with lotion. I found people pumped first and asked questions later. And several times well meaning people added soap to my lotion dispenser. UGH!!! At least a NeverMT would stop that problem. But I found the lotion dispenser drove me nuts more than it helped. I'm just going to put out a pretty lotion dispenser in this kitchen. As far as mixing the Waterstone air switch and filtration faucet with another brand of kitchen faucet, it is just going to depend on what you pair it with. As long as they look good together, should be fine. It's totally going to depend on what finish you use and the quality of the other faucet, so hard to say.

Good you remembered about cutting out the plywood underneath where the holes will be in stone, Sylvia. Your plumber will thank you!!! Faucet on 1-3/4 sink is placed centered directly above the bowls bridge divider. Soap dispenser is wherever you want, but make sure it can reach/pour into sink. Air gap (most of CA requires one) on same side where your dishwasher is is best. (I put mine in between faucet and soap dispenser.) Spacing of my 3 holes is not equal, with air gap and dispenser closer together than space from faucet to airgap. Distance of holes from edge of stone = your installers will know where to. Sink to counter front edge distance is usually 3-1/2 to 4 inches. Won't your sink opening in granite be already cut out at fab shop? Hope so - less mess and a nice finished/polished edge assured. (They cut sink cutout in plywood using in-place granite slab as pattern, then remove slab again.) Good luck to you tomorrow.

Or, get a "batch feed disposal" for which there is no switch needed. The batch feed disposal is operated by its lid - push down the lid, the disposal turns on, pull out the lid, the disposal turns off. It is also safer, since it cannot be operated without the lid on. No need for an air switch or a switch in the wall for this disposal. When the disposal is not being used, the lid acts as a regular sink strainer. I recommend the Waste King 3/4 hp batch feed model 9900TC which comes with 10-year warranty (that is the 3-bolt mount style). Or the 5000TC which is the same 3/4 hp batch feed but is the EZ-mount style. Insinkerator also makes a batch feed style, but I don't like the magnetic lid it has, which is more finicky to turn on and off than the Waste King.