I have changed both tires of my RX3, and the CST inner tubes are of good quality.
However, even a good inner tube can occasionally be damaged during installation at the factory. Therefore, I suggest you check the tire pressure regularly. If you aren't losing any tire pressure, I'm confident your inner tubes are in good condition.
I don't have any experience using either Slime or QuadBoss, so I will defer to the opinions of others on that topic.
P.S. Thanks for posting the great photograph from beautiful Chile.
__________________
Spud
"Never argue with an idiot. He will drag you down to his level, and beat you with experience."
Mark Twain
2015 Zongshen ZS250GY-3 (RX3)
2006 Zongshen ZS200GY-2 (Sierra 200)
2005 Honda XR650L
2004 Honda CRF250X
1998 Kawasaki KDX220
Mods made to my Zongshen ZS200GY-2:
http://www.chinariders.net/showthread.php?t=6894