Want to visit Prague-Vienna-Budapest in any order. Guided tour 2 days in each city plus 2 days for free lancing. Want to travel between cities by high speed rail. Suggestions regarding rail travel are welcomed. May need customized tour. Looking for recommendations of tour companies. Anyone heard of or used Firebird Tours? They seem highly rated based on traveler reviews and have been promptly responsive and willing to customize.

For information about how to go from city to city, consult rome2rio.com -- just be sure to click through to the underlying links, as the main web pages aren't sensitive to seasonal variation in schedules.

Unless you have very specialized interests, I'm not sure why you would need a customized tour. And if you want to take tours, by all means - do! But FWIW, each of these cities is very easy to visit on your own.

I appreciate the suggestion to tour each city on our own. We are not averse to that but likely a guide will know a tour guide would more efficiently highlight the major attracions and we would have days to wander and find local color. Also a great tip on train travel. Thank you.

For info on train travel in Europe consult https://www.seat61.com/index.html. Do not take Rome2Rio's suggestions at face value, they always need to be checked. A good guidebook will highlight major and minor attractions, and you can read it in comfort beforehand.

<< Guided tour 2 days in each city plus 2 days for free lancing. >>

Is that a total of 8 days or 12 days?

Does that include your travel days arriving in Prague and departing from Budapest?

For rail travel between those cities check:
https://www.seat61.com/trains-and-ro...a-by-train.htm
https://www.seat61.com/trains-and-ro...t-by-train.htm

When choosing between Czech/Austrian Rail and RegioJet railways from Prague to Vienna..
RegioJet trains run less frequently but offer 1st class experience already in booking class "Relax" (wide seats, 2-1 configuration) and sell on-board food and drinks at rock-bottom costs (50c to €2)

But neither Prague-Vienna nor Vienna-Budapest is a high speed line.. trains won't go much faster than 160kph/100mph.
Nevertheless, it's still faster than any other type of transport between those cities.

Regarding guided tours vs. self-guided walks:

In both Vienna and Prague, the major sights are really close together in or on the very edge of the historic pedestrian-only city centers.
Even the usual hop-on/hop-off buses are more or less useless in both cities because of that, IMO.
There is nothing wrong with taking a guided walking tour in either city, though. You should find many options on each city's tourist info website.

Budapest is a bit more spread out, IMO.. the HOHO bus *can* be a good start to get a feel for the city. It also goes up to the castle district and the citadella viewpoint. Another tour could be a short 1-2hr cruise on the Danube (no need to pre-arrange that).

We are planning the same trip, but will have 14 days. Any recommendations on another city that is close by. We would love to go hiking. Also, restaurant recommendations would be greatly appreciated