So, my grandpa is really bad with technology but is interested in things like Netflix or HBO go because our local TV has been shit lately.
I've helped him set up a normal Chromecast but he's having trouble with the HBO website so I wanted to ask if it's possible to control almost everything about it with just voice
The voice controls are good, and I've made it my only streaming device, but it does not pass my Retired Mom test. Even with the voice commands, it is just a little too fiddly and does some unexpected things. I think the home screen/Google TV launcher would confuse the crap out of an old person, as it shows tons of stuff you aren't actually subscribed to.
Personally I'd recommend the Roku Streaming Stick+. Best yet if you can preconfigure it before you give/send it to him. I did that with my mom during the pandemic and it worked like a charm, she just plugged it in and everything worked.
Using a remote is much, easier unless he has manual dexterity issues with his hands. Trying to remember what to say and saying it the correct way the first time is very frustrating. A combination of the remote and voice can cut some steps sometimes. You can try the CCwGTV but honestly I would get a Roku for an elderly person that's averse to using devices. Mainly because the UI is so simple with everything easy to identify with almost no learning curve.
You may want to consider using At&tTV. Their box/remote is easy to use & has voice. It opens to live tv but their guide has Netflix & HBO Max built in so he can even access them from there (free yr of hbo/HBO max for Choice pkg & above).
A Chromecast with Google TV or horrible old one that he'd have to try to control with a phone?