Hi vinky, and welcome to MySwissAlps!
>> Would like to check on the difference between getting a 2 country Eurail pass and switzerland travel pass.
You can download maps showing what is covered by each pass.
As explained in the legend on the maps, red lines are trains, yellow lines are buses, black lines are cable cars, white lines are boats. Solid lines are free, dotted lines are discounted. Discounts are mostly 50%, but only 25% for transport where you see the number “1” inside circle near the dotted line. There are a few grey lines on the maps as well, which are different for each pass. These indicate transport that is not covered by the pass.
Swiss Travel Pass coverage
http://www.myswissalps.com/sw isstravelpass/validity
Eurail Pass coverage
http://www.sbb.ch/content/dam /infrastruktur/trafima ge/karten/karte-geltungsbereich-InterRail-EuRail.pdf
>> Is switzerland travel pass included in the Eurail pass of Switzerland is one of the two countries selected in the Eurail pass?
No, the Swiss Travel Pass and a Eurail Pass that includes Switzerland are two entirely different products. The coverage maps I mentioned above will allow you to compare them.
>> If just celebrated 26 yo birthday at point of travelling, please advise if still consider youth for eurail pass / switzerland travel pass?
If you have turned 26 before or on your first day of travelling, you will need to buy an adult Swiss Travel Pass, as the Swiss Travel Pass Youth is only valid for youth aged between 16 and 25. Are you able to start your trip and/or start the validity of your pass a day or two before your birthday instead?
See this thread:
http://www.myswissalps.com/fo rum/topic/youth-travel-pass-turning-26
The Eurail Select Youth Pass is valid for youth aged between 12 and 27, so you would qualify for this.
Alpenrose