To answer your questions
1. You can install any cia. There are legit cias and regular cias. Read the sticky for more info
2. Yes
3. Yes
If you have a GW, you might as well use it. Although Rxtools now supports autoboot from startup, which is awesome
CFW and GW support the same stuff. Except GW supports .3ds files, region free, and region free dlc. Apart from that, they are the same
Sorry if this sound noob but does CFW (rxtool/cake/reinand) not support regionfree cia/dlc? I'm new to CFW things and was going to install CFW on my n3dsxl but now maybe I will stick with GW.