I spent
a lot of time researching this space before committing to a Caseta system. I came to realize these important truths:
1. Lighting control is a
subset of home automation. While many lighting control systems blur the lines by offering more functionality than just lighting, true home automation will require an overarching whole-house system (i.e. Crestron, Control4, etc) to tie all of the pieces together. While Homekit aspires to simplify this, there's considerable debate in the pro world whether this will ever truly become a reality (though it will certainly raise the bar for most people).
2. Compatibility. If you ever choose to go the whole-house automation route, all of the major automation systems are compatible with Caseta so you can just layer it on top. Caseta controls the lighting sub-system and the whole-house system controls it. In addition, Caseta
works with many other systems.
Make sure you get the Smart Bridge Pro. For the extra $50 it gives you a lot more integration options down the road.
3. From a hardware standpoint the Caseta system is rock-solid and reliable. While some of the competing systems are flashier, when it comes to the fundamentals (i.e. dimming, switching, wireless connectivity, etc), you really can't beat Caseta.
OK, on to your questions:
1. There is no overlap between PRO devices--they are functionally different so only use them where you need them. Take the dimmer as an example: the PRO version supports a mechanical 3-way switch and 1,000W (vs. 600W for the regular dimmer). If you just need an on/off switch then your only option is the PRO switch.
2. For best results you should use the Smart Bridge over Wink. To get Homekit functionality you would still need some other device/hub/etc, but honestly I'm not sure what your other options would be. It seems like the Smart Bridge checks all of your boxes, so that seems like a no-brainer to me. As to your other questions...
For local control (i.e. not attached to an automation system) you can mix and match Maestro products. That's what I did in my bathrooms where I wanted to control my exhaust fans with a timer switch. Also, I didn't see a reason to spend the money to be able to control my exhaust fan light from Caseta. This seemed like a local control-only kind of light so Maestro was perfect. I also used a Maestro motion sensor dimmer switch in my powder room so the light come on when you enter the room. Again, I didn't see a reason to use Caseta here. You can see some finished pics from my installation at the thread linked below:
https://forums.lutron.com/showthread...ation-COMPLETE!
Hope this helps!