So, my order has been placed (so, I'm jumping into the deep end) and while I am awaiting delivery I am trying to get everything prepared - well, as far as I possibly can.

@nieldk, I am so grateful for your step-by-step description. It really cleared u a lot of things for me

May I still ask a few stupid questions?

Is the oos2.2.1-x.zip you mentioned identical with the OnePlusXExtraPartitions-2.2.1-X-0.zip I downloaded from https://forum.xda-developers.com/sho...91&postcount=1 (I got there through the link you provided - https://forum.xda-developers.com/sho...91&postcount=1 )? I know it probably is the one you meant. But I just want to be absolutely sure not to cause damage by accidentally having picked the wrong file.

For step 5 do I use the TWRP version linked to from the merprojects wiki https://forum.xda-developers.com/dev...t/dl/?id=15644 or the one from the general instructions here https://forum.xda-developers.com/sho...3&postcount=45 ?

Do I need to adjust any settings in TWRP at any point, like erasing parts?