All the segments in your itinerary are rather easy to accomplish, but it will be good to know the exact number of people traveling, since for instance Czech Railways give a special discount for mini groups (2 or more passengers) or in cases when it's family you it is possible to take an advantage of passes like CD-NET and SONE etc., thus in order to compare bus vs. train it's good to know all such potential details.
Nevertheless:
a) in case of Prague-Cesky Krumlov journey you can get train ticket for as low as 180 CZK per person (when purchase some time in advance via Czech Railways
eShop). There are some bus operators that can give you even better per person fare, but choice (whether to go by train or bus) anyway is yours. Train is around 3:40 (with one change in České Budějovice), while buses are direct and take around 3 hours.
b) Cesky Krumlov-Telc train ticket cost 170 CZK (again in advance purchase via CD eShop), total journey with at least 2 changes takes form 4 to 5 hours (depending on connection). Bus here is actually cheaper and faster, for instance dep.8am from Krumlov, arr.České Budějovice 8:55, change there for a bus to Telc, where you'll be 11:00 and you pay total of 127 CZK per person
c) Purchased in advance Telc-Olomouc train ticket cost 220 CZK per person, again at least two changes (Kostelec u Jihlavy and Brno) and around 5-5:30 hours in total. While by bus the same route can be managed a bit faster 4-5 hours (depending on connection) and cheaper, from 187 CZK per person).
d) Here cheapest train tickets start from 190 CZK and journey is direct and fast (from 2:30 hours), while bus ticket start from 220 CZK and ride takes at least 3:30, but in most case more than 4 hours
All the train timetables for Czech Republic can be checked on
Czech Railways website, while in case of buses you can do the same
here. In case you have any further questions, feel free to ask.