Best smart upgrade I've done is easily replacing all of my light switches with Lutron Caseta's. Definitely do this over the smart light bulb route if you own your home. The light bulbs all are an individual device that require wifi connection, and they're 2.4ghz, and even the best ones drop connection sometimes. Lutron switches only have a hub to connect to your network and they communicate with each other with some proprietary technology that has been working flawlessly for me for the year or so I've had them. I don't know how they work, but they do.
Lutron has dimmable and non dimmable switch options, and neutral wire and non neutral wire options, which is great if your home is older. They have switches that turn ceiling fans into "smart" devices (as in you can control the fan with the app or a Google home/Alexa/etc) without needing to do anything to the fan, which is super handy. They also have wireless remotes which I've mounted in places I really wish had switches but don't, like the hallway to the downstairs bathroom only having a switch on one end for some reason. You just mount a wireless remote, program it in the app, and nobody can tell it's anything but a wired switch that is supposed to be there. I love them.
Not exactly a smart home upgrade but if you want mesh WiFi I've tried a ton of them and my favorite is hands down Plume SuperPods. Most stable wifi I've ever experienced by a landslide. Little pricey compared to other residential level equipment, and not as good as installing enterprise level Ubiquiti or similar gear, but damn good. I get ~850mbps or so everywhere in the house with 3 pods (2 floors, 2k sq ft) but they'll help you decide on the needed amount and optimal placement if you contact their support.
I have a Chamberlain MyQ and I barely use it, but one thing that is nice is Amazon will deliver packages into your garage if you link your MyQ to your Amazon account (it's called Amazon Key). If you shop on Amazon a lot like I do and have a porch pirate problem, it's actually pretty great.
For security cameras check out Wyze. Very solid equipment for a very reasonable price. They sell wired and wireless.
Robotic vacuums - I have a roborock S5 and it's amazing. Has high end features for a mid range price. It's probably spying on you if you use the default app and firmware, but flashing it to Valetudo RE is easy and disables it's ability to phone home to China. Mine is also modded to replace it's audio with R2D2 noises and I found a nice set of R2D2 vinyl stickers online for it.
I have Nest thermostats on each floor and in NC the local energy companies offer them very cheap if you buy through them, I'd look into that in Ohio. I got both of mine for $49 each through Duke energy and they're the full featured version. They are well worth it at full price. You can voice control or app control the temperature, and they do save you money if you use the eco mode.
I control everything through Google assistant and have several displays throughout the house. A big one in the kitchen is super handy for googling recipes or YouTube videos for cooking and having it right there and controlled by voice so you don't have to stop and wash your hands to look something up. I use the one on my nightstand for sleep tracking, an alarm clock, and a thunderstorms/ocean waves machine. The interface is actually pretty nice if you prefer a touch screen over voice controlling everything.
I have Nvidia shields on each TV which are also capable of being controlled by Google assistant and have chromecast built in. It's nice to just say hey google, turn off the TV when the remote isn't nearby and you don't want to get up. Streaming to the bedroom TV from the PornHub app has come in VERY handy on several occasions too lol.
I have Nest protect smoke alarms too which are hooked up to my security system, so if there's a fire and I don't respond to the alerts it will call the fire department for me. Everything I have controlled by Google assistant is synced to my alarm system by syncing them together in the Google home app.
I've got a WiFi enabled Denon receiver for my home theater that is also controllable through Google assistant, and you can stream music to it from your phone which is also quite handy.
I've got a smart lock with a touchscreen pin pad, finger print scanner, and video doorbell called the Lockly Vision on my front door and one without the video on my back door. Both are battery powered which is great because my house wasn't wired with a traditional doorbell and most video doorbells require them for power.
I'm not sure what else I'd even get at this point, I feel like I've optimized everything that would actually improve my life. I don't have any smart appliances so I can't speak on that, but maybe in the future.
If you've got a much bigger budget than I did and want to have someone else set it up for you, I've heard great things about a product called Control4.
I've tried out home assistant and didn't like how much customization it required. I'm a pretty big tech nerd - I wired my house with ethernet and serve 4 rooms with a media server I built in my network closet if that gives you any idea - and it was too much for me. But it is very popular among tech enthusiasts.
Hopefully some of that helped you.