step 4 - yes, running haxchiFW lets you get into homebrew without having to go through the browser exploit every time, saving like 2 minutes every time you boot up your wii u. its totallty worth it and safe but you would need to buy a $7 game (brain age, etc) from the eShop to "take over". The only homebrew I run really is the WUP Mod Installer Y to actually install games downloaded from uTik.
step 5 - if anything redNAND is less risky, since you are dumping your firmware to your SD card and then booting off that from now on, leaving your system firmware untouched forever. If you ever fuck up no big deal, take your SD card out and boot into regular firmware and redo redNAND with a new sd card. You can use a single SD card, it just shrinks by 32gb. I use a 128gb card, which turned into 96gb (90gb really), about 5 gigs of that is used up by various software, leaving me 80 gigs to install games and stuff with. 64gb card would be just fine too but you'd be able to only install 1-2 games at a time, remove card, delete, recopy, etc. After you install all your games though its not like you are gonna do much more with the SD card.
I did the whole kit and caboodle including coldboot, I say why not - there are zero new wii u games coming out, its nice turning on the wii u and booting straight into mocha and being able to run anything without remembering steps to do before. It only adds maybe 20-30 mins of extra file copying.
You don't have to deal with loadiine or nnupatcher at all, I don't think I even copied those things over. utikdownloader is all you need. saviine I think lets you copy save files around. NTR is eventually nice to have if you want to cheat in games or mod them, like adding skins in SSMB or MK8.