1: yes, 2: technically yes, because you are writing to nand, but in practice not really. the unlaunch installer has proven itself reliable over the last 5 yearsCan I mod my DSI-XL on it's final firmware 1.4.5, Does it has any risk of getting bricked?
where it could brick is if your nand is almost at the end of its write cycle life time, and one extra write for installing unlaunch ended up pushing it and making it fail, but then you would likely run into the same problem just using normal dsi functions anyway. once unlaunch is installed you never need to write to nand again after that, either you use twilightmenu and everything happens on sd, or you use hiya and everything also happens on sd.
I mean, you can also use normal dsi launcher with unlaunch installed, and have dsiware and forwarders on the official launcher and everything, but if you were concerned about the possibility of bricking because of nand writes, then unlaunch will give you the tools to mitigate this