I don't understand the question. Is what "necessary"? You never need to edit the INI file but you can choose to if you like.
If you don't edit the INI file then you control when the texture packs are loaded by the placement of the matching ESP files in your load order. So mods can still override them.
If you edit the INI and force the game load those BSAs then you will not need (and should not use) the matching ESP files and any other mod you have will override their textures.
And those instructions are broken. There are three (not two) BSAs in the texture pack and you should be adding them to the end of the sResourceArchiveList2 list if you're going to use the INI edit method. The INI file your game uses is always in your Saved Games folder (or wherever Mod Organizer stores it if you use MO). Either edit that file or create one called Update.ini or a name that matches any of the ESP/ESM files you have loaded (but not Skyrim.ini) in your Skyrim\Data folder and use it to load the texture packs. The entry you need goes in the Archive section.
[Archive]
sResourceArchiveList2=Skyrim - Voices.bsa, Skyrim - Voicesixtra.bsa, HighResTexturePack01.bsa, HighResTexturePack02.bsa, HighResTexturePack03.bsa
cd.... he's following religiously the instructions in the STEP guide....
here how the game loads files :
1. Ini files
2. esm
3. esp
4. Loose Files
Eh, I was just going off the last bajillion posts from him. As for using MO.... um. No thank you. WAY too complex and I've been managing complex applications since 1985.
No, you won't. I LOVE NMM. I didn't like it a couple years or so ago, but I do now. I've read the docs on MO.... and believe me I'm no dummy when it comes to software.... but sorry.... it's not for me.
[You really need to look at this guy's post history. He's not asking the people who manage STEP - he's asking here.... What does that tell you?]