I find KDE connect to be both useful and interesting to use. It’s not really recommendable in and of itself but it makes connecting between your various devices very effective, like file transfer, clipboard sharing, remote control etc.

With regards to casual gaming, I personally don’t have anything to recommend because that’s exactly the kind of game I try to avoid. I like involved games, interesting, with a story, a purpose, requiring thinking and such. But what I can say is that the steam deck is so effective with its sleep functionality that you can very casually play any involved game no matter how much time you have.

It is so easy to be back in the game: I’ve played the witcher 3 a lot (highly recommend it if you have not played it) and it is a very involved game, but I’ve been in and out for even just a few minutes thanks to sleep. It takes one second to be back in the game fighting some enemies and takes a second to pause the game and put the console back to sleep in my backpack. You don’t have to restrict yourself to casual games to benefit from casually playing, with the steam deck.

My boring advice is to spend a few weeks using it as it is out of the box: just play your favorite games on it.
After a while you might get a sense of what you would like to change (if anything) and then you can research how to go about it.

For casual games on the Deck some my most played are The Binding of Isaac (most hours by far), Brotato, Deep Rock Survivor, Slay the Spire, Balatro, Dead Cells, Crypt of the Necrodancer, Shotgun King. But there are so many good choices, it really depends on your taste.

I also only got my first deck last month a d went through a similar though.

I’d suggest:

• Play with it a bit stock. It’s a great experience and you really don’t NEED more.
• If you have any interest in playing older consoles, Emudeck is an amazing experience and worth it for the ‘oh wow’ factor
• Add Plex / streaming though flathub/discover and add to steam for travel streaming
• Consider decky for a few QOL menu additions
• For pick up and put down games review threads on indies for games you’ll love. Balatro, Hades, Dave the diver, dredge, undertale, into the breech, FTL, the list is quite long and there are utter gems, but it will be dictated by what you enjoy

Only useful for desktop mode, but KDE Connect is great for syncing clipboards, sharing files, and even remote mouse and keyboard input between a smartphone and the desktop environment.

It’s a game changer compared to using the touchscreen keyboard. Especially with a dock using it as an occasional media PC.

A thing to do: Look up how to install Nested Desktop into Gaming Mode (a quick YouTube video will show you how to set it up in about two minutes). In short, it allows you to access most of the functionality of Desktop Mode when you need those things, without actually having to officially switch over (think of it as Gaming Mode’s Desktop Mode Emulator).

Saves you bunches of time in the switching back and forth, as it’s almost instantaneous. I use it all the time, as stuff like web browsers also work better on the Desktop side.

As for casual games you can play for short bursts and put to sleep whenever… you already mentioned Balatro, that’s a great one. I love roguelikes and deck builders for this purpose in general. Recently, I’ve been playing a ton of Cobalt Core, I’d highly recommend as a great pick up and play and quick stop.