Welcome to the Hubitat Community!
OK, VC discussions aside, let's get the thread back to your questions. I will agree with most of the recommendations here. Lutron Smart Bridge Pro is a no brainer if you already own Lutron. Get one, you will not regret it. Pico on HE is just awesome. You can control anything and even smooth dim smart bulbs.
Take your time with the other things. Don't be in a race to fill out your home. If you're frugal like me, you won't be (although I'll admit to a Xiaomi addiction; More on that later).
You are smart to move away from WiFi. It's limited, a pain and just helps to increase attack points. No sense in putting yourself on a local hub, and then having some rogue WiFi device expose you to all kinds of trouble.
I have no horse in this race, but I will echo the suggestions to lean toward Zigbee. And I fully expect the counter Z-Wave fan boy posts to follow. I have both and they're both fine. But, I have only two Z-Wave devices. One by choice so I could learn more about Z-Wave locks and Z-Wave Plus, and my Home Energy Monitor that I use for monitoring the current status of my washer and dryer is Z-Wave, simply because Zigbee wasn't an option for that device. Both have been fine. My lock, a Yale YRD256 Z-Wave Plus, unlike some of the complaints about the Z-Wave Plus version, has been absolutely exemplary in every way. I highly recommend that lock in either Zigbee or Z-Wave Plus. My HEM, an older Z-Wave device (not Z-Wave Plus), will lose connection from time to time (more rare than anything), but I have no Z-Wave repeater, so I do not complain about that.
Keep Zigbee lightbulbs off the main hub, unless they are Sengled. Every other Zigbee bulb brand will try to repeat the Zigbee signals to strengthen the Zigbee mesh network, but they will instead drop data packets or get turned off by accident, causing havoc with the Zigbee network. I recommend Hue and IKEA Trådfri bulbs (for a more economical choice), but only attached to a Hue Bridge, or a second Hubitat Elevation hub by themselves so that the bulbs run on a separate Zigbee network, unable to screw up the mesh for the other Zigbee devices. Sengled bulbs on the other hand are the only one that don't try to repeat the Zigbee signals, so you can add those to the main hub with no concern over destabilizing the Zigbee mesh network.
Devices are definitely not created equal, and everyone has their favorites; some are failrly equally despised. I mentioned my Xiaomi addiction. It exists because they are inexpensive, nicely designed, high quality, very small, responsive and great on battery life. The community drivers are fantastic and with a stable Zigbee mesh and adequate compatible repeaters, they are as stable as anything else I own. It is absolutely true that users were suffering stability issues due largely to the lack of compatible repeaters, but also due in part to them not fully complying with the Zigbee 2.0 standard, and it wasn't uncommon to have to reset them every so often when they dropped off the network. But as mentioned, the Zigbee 3.0 IKEA Trådfri outlet and the dedicated Trådfri signal repeater are both "Xiaomi priced" (e.g. Super inexpensive), and compatible with the Xiaomi devices for repeating signals. The community has tested a lot of devices with the current line of Xiaomi devices, and the list is very short. The easiest to get for most people, least expensive and relatively consistent are the Trådfri outlet and repeater. The strongest, but not easiest to get started with. and a bit costly to obtain, is an Xbee. The Xbee serves a second very good purpose (among others potential uses), and that is to show you a map of your Zigbee network so you can check the routing and health of your Zigbee network and devices. An Xbee is by no means a requirement, but it definitely is a "nice to have".
The new Xiaomi Aqara Zigbee 3.0 devices (most) will have a T1 suffix in the product name. Maybe they will fully follow the Zigbee standard. Who knows for sure at this stage? Either officially or unofficially, we're going to be able to use them here. The suggestion I would make however, is to wait for availability of the T1 line next month. They have to come direct from China to get the really low prices, so you can expect to wait another two weeks to a month after ordering to get them. But the currently available devices are really inexpensive, so I wouldn't hesitate to buy a few devices and a couple of Trådfri outlets and/or Trådfri signal repeaters right now to play around with. A leak sensor is a good start. Serves a great purpose and introduces the product line to you. Here is the list of compatible devices. Most of the Xiaomi Mijia and Xiaomi Aqare products work just fine with the same driver. I would only suggest to avoid the round Mijia temp/humidity/barometric pressure sensor, and instead buy the square Aqara temp/humidity/barometric pressure sensor. Also, the Xiaomi Mijia contact sensors are the more stylish rounded one, so if you're not going to wait for the Zigbee 3.0 Aqara contact sensor T1, then the Mijia work equally well and are a lot better looking in my opinion.
Have fun. Don't be in a race to "complete" your system, and don't over-spend on expensive product thinking the price is going to get you reliability. That's definitely not a hard and fast rule. Three places I purchase Xiaomi Aqara and Mijia devices from are Gearbest, Banggood, and Ebay. Prices vary wildly, so shop all three. You can also find them on AliExpress, but I don't particularly like using my credit card on their site, whereas Gearbest and Banggood accept PayPal. Sometimes (rarely) I will buy from private sellers on Amazon if it's just a few dollars more with shipping and I am guaranteed to get it faster. But read their listings carefully. I've had more trouble with private sellers on Amazon than I have on Ebay.
