It doesn't really feel like an update, though. Imho, sections make it easier to create a dashboard because you can move things around easily until you find the perfect layout but if you already have the perfect layout, they're not making things easier for you.
There are few advantages i think. It is predictable, the cards do not change flow order. It is flexible, you can configure layouts with different column sizes, with was not possible with native cards. It is plug and play. And there are some new features, some adding today, that are pretty cool.
To copy your grid card with rooms, you could copy it over (just like you did initially) and then edit the yaml of the new section (yes you can do this) and carefully remove the yaml of the surrounding grid card. This will leave just the individual template cards.
That's a rather old Wemos D1 with a Dallas sensor, configured in ESPHome. I made that one like 5 years ago, still works, quite well. The sensor is on a long wire, I zip-tight it in the skimmer. And the microcontroller is in the pump compartment. I originally also wanted to measure Ph, but never did that, I think it is quite tricky, the sensor need to be calibrated regularly, so I measure that manually :(.
