It's extremely similar to Divinity. The combat system is based on D&D 5th edition, so there is less teleporting people onto flammable surfaces and setting fire to them, but it's still similar enough to be called a spiritual successor.

I'd say it's feel very similar. But the system is based on D&D 5e. It feels slower and more restricted. Still super fun.

I'm not familiar with 5e stuff and I'm having a blast.

I've just started playing on steam deck about a week now. Overall its great and well worth it. it very much feels like the originals, but modernised with more options and choices. So long as you have the 100GB or so free.

As others have said, a few bugs in quests and stuff- probably more than i expected for a game that been in beta for a long time.
Save often and be prepared to go back.

Specific issues to (my) steamdeck - I've had a few graphics crashes at first.
It's supposed to run in dx11 mode on steamdeck, but I think mine was launching in vulcan for some inexplicable reason.
I have stable up to date system, and i got it straight from steam - so it should be fine.
Vulcan a bit unstable even at low setttings - playable, but annoying and low is a bit too blocky.
All the fixes on line talk about a "launcher" that doesn't exist any more.
It was hard to find relevant help and ignore the issues for windows and pre-release circumstances.

In the end I figured out I had to find the launcher.sh config file and manually edit it to point to use the dx executable.
Pretty simple fix once you know that's what you need to do.

Switching to DX11 seems stable on medium settings (40fps locked) and no crashes so far.
I've not tried higher gfx settings yet - I don't really care about high - medium is great.
it's pulling about 12W give or take, at medium - so you might be looking 1-2 hours tops on battery.

Playing experience is pretty good on the steamdeck controls.
I was fully prepared to have to use mouse, but haven't needed to.
I had to get used to the radial menus, but I've not even bothered mapping the back buttons to anything yet.
The interface has obviously been designed with a lot of thought about console controllers.

I'd say go for it - i think most people do not seem to have a vulcan issue - otherwise there'd be more comments about it - and it can be fixed easily enough

It's basically DOS3 with different combat, better dialog mechanics and generally better designed. The way exploration, stealth and general flow is essentially the same as Divinity and will play very much the same way, with some improvements on most areas.