Further notes about horse power:
The original privilege to build the horse railway stated that a single horse should be able to pull 10 times more load on railway than on road. The official test proved that it can pull 30 times more. There's a picture of 2 horses pulling a road waggon loaded with 12 barrels (of salt), and a single horse pulling 3 rail waggons with 40 barrels each. So really 10 times more. Another picture shows 2 horses pulling 5 waggons. Other pictures show passenger transport with one coach pulled by 2 or even 3 horses (that was probably on the steepest part of track). Another report says about 2 horses pulling 2 waggons form Budweis to Kerschbaum, but then it was split in two for the descent to Linz. In general, all trains on the southern (steeper) part were split in two, and had extra horse for the steepest (>2%) part. More pictures here:
https://de.wikipedia.org/wiki/Pferdeeisenbahn_Budweis%E2%80%93Linz%E2%80%93Gmunden.
One of the very first rides on unfinished railway was documented: 2 horses pulled 7 waggons with 14 tons of load "easily" at 30 km/day. Downhill towards Budweis, probably without changing horses, so they had to have a rest.
Passenger trains took 14 hours to travel the whole line, with 1-hour lunch break in the middle. (avg speed 10 km/h).
EDIT: German wikipedia says average speed 10 - 12 km/h erreicht, maximum downhill speed 15 km/h.
Cargo trains took 3 days. On the steepest part (2.17 %) they needed 2 horses to pull 1 waggon with 2.52 t of load.
Average over the whole line was that one horse on railway pulled 3.92 tons while one horse on road only 0.56 ton.
I could not find how fast were the cargo trains. But the timetable was that at 5 AM a passenger train departed from Budweis. Only after that they could load, assemble and dispatch a cargo train. It arrived at 10 AM to next station Holkov, changed horses and continued further on. Horses were fed, had a rest, and at 2 PM, another cargo train back to Budweis was dispatched. It had to arrive and unload before 7 PM when passenger train from Linz arrived. So I think the train must have gone the 20 km to next station in at most 4-5 hours, i.e. 5-4 km/h (EDIT: german wikipedia says 4 km/h average speed for cargo trains, and 40 km/day - no traffic during night)
Amount of horses for each train was dependent on the gradient of the section to the next station.
They needed 2x more horses for the southern half of line than for the northern.
In 1846 they experimented with oxen but not sucessfully.
In 1854 they experimented with steam engine on the wooden rails, but it was too heavy and damaged the track.
Another old report says about one horse pulling 100 barrels of salt downhill towards Budweis.
Some bridges were wooden, as there was a report of sabotage by burning a bridge. Other bridges were stone viaducts and survived today.
Fix about loops - there were stations every 20-22km where horses were changed (both cargo and passenger trains), but later some extra passing loops were added, probably every 7-8 km.
1868-1872 track was rebuilt for steam operation
And that's all I found in the book and other sources about this line