Dtm = digital terrain model. The measure preceding it is the effective size of each pixel in the data. So 1m DTM = 1 pixel is 1 meter. 30m DTM = 1pixel is 30 meters.
A DEM is a digital elevation model.
In most places these 2 mean the same thing.
In America they don’t, the DTM is a vector representation of ridgelines and streets that complements the DEM.
So yea, you would want a 1m DEM. And yes they are super rare.
Grass Gis can probably help lessen the terracing effect. I have to really look into it myself since the areas I want barely have 50m DEMs…
Either way, making the 30m dem 1:1 is not so bad. You can run the smoothing tool over it (low stenght) manually and solve most of the terracing within the playable area. The further out the landscape gets the least the terracing will be visible (to some extent though it will always be visible since every 30 meters will be 1 pixel of data).