We have twice planned a visit to Caserta but had to cancel both; the first due to the pandemic and the more recent one (2024) because a hiking tour we booked in Abruzzo was canceled and we moved our trip to northern Italy. but I will tell you the places I had booked.
For March 2020 I booked a bed and breakfast, the Artistic Charming House, which has lovely rooms and very high ratings on booking.com, though it is a bit further from the train station than I wanted. For 2024 I booked a new hotel that did not exist before the pandemic, Hotel Europa Art Caserta. This is a more traditional hotel and closer to the station and the palace entrance. It also is highly rather on booking dot com (which I like to check for reviews and ratings before I book directly with the property.)
Maybe one of these will appeal to you. If not, there are lots of other places; Caserta seems to have responded to the tourism boom and now has many more accommodations listed than I saw for 2020.
As for a stop on your way north to Padova, you could certainly take the fast route with Frecce trains with changes at Rome and Bologna, and few stops along the way. If you choose that route, I would suggest an overnight in Ferrara, which is a lovely city that is not overrun with tourists, and has a much easier train station to navigate than Bologna. If you choose Ferrara, I highly recommend Hotel Annunziata, a family-run hotel on a little piazza across from the old castle (with a view of the castle from some rooms). The main piazza of the town, with the cathedral and a large pedestrian/shopping zone, is just through an archway.
But if you are thinking of something more off the beaten path, but still a direct route with few train changes, you could go up the Adriatic coast and stop overnight at one of several towns and port cities along the way. Here is one option:
FA 8303 departs Caserta at 9:14 am, bound for Bari in Puglia. You leave the train at Foggia at 11:05, before reaching Bari. Then catch a northbound train that runs along the coast. IC 610 departs Foggia at 11:10, or if that is too tight a connection (it would be for me, in Italy), there is FR8820 at 11:36.
It is about 40 minutes’ ride to Termoli on the coast of Molise, a small walled town with a Swabian (Frederick II) castle and nice beaches. If you stop here you will probably be the only person you know who has visited Molise.
https://molise.guideslow.it/estate-a-termoli/
One of many possible places to stay:
http://www.locanda-sangiorgio.it/en/
Next day, you board FR 8816, a fast train which goes to Padova with no further changes. Which means you do not have to change trains at Bologna Centrale, which can be confusing.
If Termoli doesn’t appeal, you can stay on the FR8820 from Foggia and stop at any of these seaside/port towns: Pescara, San Benedetto di Toronto, Ancona, Pescara, Rimini. Ancona appeals to me for the sea caves, so I put it into one of our (canceled) trips;
https://anconatourism.it/en/places-you-cant-miss/passetto-caves/
The SeePort Hotel was very kind and understanding when I asked to cancel. They have modern rooms with a beautiful view over the sea and if we get to visit Ancona I would book there again:
https://www.seeporthotel.com/en-GB
On a trip we did not have to cancel we stopped overnight in Rimini, and were pleasantly surprised. Hotel Aria gave us a very warm welcome, and the oldtown area was very enjoyable, with a Roman bridge from the 1st century still in use (by pedestrians), and particularly lovely during the evening passegiata. Rimini is known for other Roman sites as well.
https://www.atlasobscura.com/places/ponte-de-tiberio-bridge-of-tiberius
https://emiliaromagnaturismo.it/en/art-culture/art-cities/ancient-roman-rimini
The main piazza, which is well back from the famous beach, was ringed with restaurants and we had no trouble finding a nice table at one, despite no reservations.