Out of the box it works, including cloud saves.
The only thing I needed my PC for was to upgrade the SSD: I used my desktop to prepare a flash drive with the SteamOS image. Honestly you could probably do that using a USB adapter on the Steam Deck, booting with the original SSD.
It really comes down to convenience. It takes a minute or so to switch between desktop and gaming modes on the Deck. A lot of stuff is easier if you have a larger screen or two, plus a mouse and keyboard. And file transfers are faster over Ethernet. All of those things you can either work around with the Deck as it is, or you can use a dock or hub to plug in those extra peripherals, but it’s still an inconvenience unless you’re planning on using it docked often.
I’ve got much better devices for porn, but it’s pretty easy to use one-handed. Sit up with it on your lap. Lay down with your hand under it and the other side in the air, or with your hand on the top side and the other side resting the weight on your couch or bed.
If you couldn’t do that you’d need a 3rd hand to use the touch screen.
Hmmm… I wonder if there’s any porn games that support simultaneous controller and touch screen import.