Hey
here are some quick responses:
1. If you're in the EU region, and your native language is english, then Bloodiron is the PvP Shard to go. If you're in the US region, then Seastone is the shard you're looking for. Here is a full listing of Rift Shards along with the corresponding populations:
http://www.riftgame.com/en/shardstatus/index.php
2. There is a mercenary system in place on rift that balances out the warfronts and speeds up queues, so if too many Guardians are queuing for example, then some of them would be placed with Defiants as mercenaries and warfronts will be balanced. In dungeons, you will be able to play with members of both factions (even if on a PvP shard, if i'm not mistaken) and because of that queues are in a good state. Rift has mostly done away with factions, so choose the faction that appeals to you the most.
3. Transfers are free and are done in game, and they are instant, no waiting at all. there is no option for a faction change at the moment in Rift, but with the changes to the game, its pretty much unnecessary. on PvE shards, guardians and defiants can be in the same guild.
Tips for Leveling: Use instant adventures as much as you can, do any zone invasions you come across, and close as many rifts as you find. 1-50 can be done in 24 hours /played time. 50 - 60 is another story altogether and currently needs at least 48 hours /played as per what some people have been reporting.
Also, make sure that you use the ascend a friend feature - it will grant your friends a trinket that increase xp gained by 20% up to level 20, and it will grant the person who initiated the invite several rewards such as XP pots (increases xp gain by 100%) and other rewards like level 50 gear currency.
Welcome to Telara.