Train from AMS airport to Bruges

The high-speed Thalys is, of course, the quickest, taking 2,5 to 3 hrs. It is, however, also the more expensive one and it comes with a compulsory reservation for a specific departure time. With the uncertainties of the arrival of your flight and the handling at the airport, that is problematic.
The safest and cheapest way is to take the Intercity Brussel, for which you don't need a reservation. A ticket is valid for any Intercity train on that day: if you miss one train, you simply take the next one. It is slightly slower: taking 3,5 hrs.
For schedules and tickets, consult the website of NS International. (Select »Schiphol airport« and »Brugge« for departure and destination stations.)

The Thalys train route from Amsterdam goes through Antwerp and Brussels on the way to Paris. If you put Amsterdam-Centraal as departure station and Brugge as arrival station into reiseauskunft.bahn.de/bin/query.exe/en, it will tell you exactly where to change to a local IC train, which would usually be Antwerpen-Centraal; although at some times of day it is more convenient to change at Bruxelles-Midi.

You would therefore normally get off the Thalys train in Antwerp and stay within the same station (which is on different levels, you will probably go up one level); there are departure boards, timetables and monitors to tell you which platform the next IC train to Brugge will leave from. If by any chance it is more convenient for your timing to change at Bruxelles-Midi this is also within the same station, just a matter of going to a different platform.

Another option is Eurolines. We did this last time we went to/from Amsterdam and Bruges and it was great - and far less expensive than the trains.

http://www.eurolines.com/

You can also purchase tickets when you arrive in Schiphol airport the morning of April 16th. The Inter-city trains don't sell out and you can't make reservations. Just follow the signs to TRAINS. The train station ins below the arrivals hall and there is a NS ticket desk just near the large red and white cube called the "Meeting Point".

https://www.thetrainline.com/en/train-times/schiphol-airport-to-brugge

The reason your answers are not consistent is that your question is contradictory.

The fastest is the high speed (up to 186 mph) Thalys train. Also the most expensive.

Your second part of your question, the bus (Eurolines) will likely be most inexpensive but undoubtedly by far the slowest.

You can't have both.

Which is more important to you?

If you are planning to head to Bruges as soon as you land, your best option is to take the intercity trains as tonfromleiden noted. Due to the actual uncertainty of when you will land and the time you will need to go through passport control, booking a thayls train is simply too risky as there are too many variables with your arrival. Booking a Thayls is basically like booking an airline ticket, the tickets become prohibitedly more expensive the closer to the departure. If you are returning to Amsterdam from Bruges, booking a Thayls may make sense if you have a set day and time you plan on returning as you would have fewer unknowns-provided you book well in advance. The Thayls train is maybe 40 mins quicker if I remember correctly, so it’s not like you are saving a huge amount of time by skipping the inter-city trains, however, it is nicer and more comfortable.