Konnected.io as others have suggested. Personally, I'm content with HSM, it's far superior to SHM on SmartThings. I live in a multidwelling property which I own, there's always someone on premises at all hours, so security isn't a huge concern to me. Still, HSM still could use a bit of added polish, including minor things like homepage status in the admin UI.
I think I've have virtually every leak sensor on the market in the past 5 years (j/k) including Everspring/Utilitech Z-Wave, as well as several PeQ, Iris v2, SmartThings v4, & SmartThings 2018, all Zigbee. The PeQ's seem to eat batteries the fastest. I like the 2018 SmartThings model as it has a collection "cup" on the top cover to detect water dripping onto it. It still has the contact on the bottom too. The Z-Wave sensors are my second choice as they have a remote probe on a 10' cable which allows you to hide the radio portion in a cabinet. Battery life is a couple years on the things too.
I've heard rumors that Google is limited access to the Nest developer program which may limit your ability to integrate these into Hubitat. For me anything Google & HA related are a non-starter due to privacy issues. I'm also bitter over how they handled the Revolv shutdown.
This is one area I wish I could have a do-over, but with investments in 8 Z-Wave locks, it is not financially worth it. My experience has convinced me that Z-Wave is just not the optimal protocol for locks. Zigbee locks always seem to be more responsive and less prone to disconnections. There was a Youtube video posted a few years ago comparing the same Yale lock against itself by changing just the radio modules.
I've never used Lutron, but this is another case where if I had it to do over I would go Lutron. I've recently had a rash of GE Z-Wave switch failures (3 in 6 months), all purchased at the same time 4 years ago. I've never had issues with the performance of Z-Wave switches, but do think the Caseta line is more aesthetically appealing.
The Ecobee has been a winner for me, So much so, that I put them in my rentals too. The API is persnickety so 3rd party integrations can be irritating, but I like how reliable it is at doing its core functions. The one in my place is about 1 1/2 years old and has never let me down.
I'm watching this thread for recommendations. I don't have any but will be replacing some window treatments this year.
The Utilitech/Everspring sirens have always been reliable for me. They're not very loud compared to wired sirens, but they fit the bill.
Link bulbs suck. Individual mileage may vary, but the consensus is usually to avoid them.
I like Hue myself. I personally don't want a bunch of WiFi light buts clogging up my WiFi mesh, I've already got over 50 wireless devices as it is. I've noticed the Hue bulbs don't play nice with Hubitat and try to connect to the hub even if the hub is not in Inclusion, requiring me to use a Hue remote to reset them,
I have a huge Arlo investment, but I'm starting to regret it. If I was to do it again, I'd use Blueiris as a back end, and some cheap PoE cameras from Amazon. I think I'd get better quality for less money.
Good luck with your new place!