You forgot the steam powered paddle steamers.
You have a choice of 3 other 750 within lines within reach of Dresden by train.
The FightelbergBahn is excellent you can get a train to Cranzal change at Floha on the Dresden Cheminitz line. Steam to Oberwiesenthal climbs from 654 m to 892 m.
Then from Freital Hainsberg on the S bahn (Tharandt) you have the newly reopened (after serve flooding) Weissernitzalbahn not yet through to Kisdorf but Dippoliswalde. Still you get the climb up the gorge crossing and recrossing the river that caused all the problems.
Then if you go Zittau, through trains from Dresden, you have the line to Jonsdorf/Oybin.
Don't know whether they still do the double departure from Bertsdorf to the two branches. Jonsdorf branch is the steeper of the two.
Should be able to do Cranzal and Zittau on Lander tickets ( up to five people Aprox E30.)
Then you've got the Kirnitzschalbahn metre gague electric tram which winds up the valley beside the road from Bad Shandau to Lichtenhainer Wasserfall. You can get to Bad Shandau on the S bahn to Schona all along the Elbe. You can use the Dresden Verbundum ticket. You can come back on the same ticket via Sebnitz to the S Bahn at Pirna. But if it's a nice day you can come back on the paddle steamer from Bad Shandau.
You can eat on the steamer so don't have to bother with dinner in Dreseden you can go straight to one of the Brau Houses.
Near Cranzal there is an excellent preserved line form Johstadt to Steinbach, the Pressnitztalbahn. They use Meyers but you need to look up when they run and probably need a bus from Annaberg Buchholz (on Cranzal line).
To plan trips try the
DB» website
http://reiseauskunft.bahn.de/bin/query.exe/en?newrequest=yes&protocol=http:&All the narrow gague lines have their own websites with timetables and fares.
Re park railway, don't forget it's right by Volkswagan factory which has the cargo trams, also I believe it tends be steam only at weekends and holidays.
Also on Lander tickets don't foget Zwicau and do the mixed gague tram, diesel railcar service to town centre. Good Brau Haus near town centre station.
Also in Dresden the Stanseilbahn and Swebebahn just over the Blue Bridge, unfortunately they are not included on the Dresden day ticket.
So if you are into public transport Dresden is the place. If you sit at the back of one of the new long trams the driver can be in one street whilst you're in another!
If you are out late it's worth going to Postplatz to watch the trams and buses all arrive, interconnect and then depart, this happens every half hour.