How to optimally end game starting from nothing?

Hi, totally new player here. I enjoy making alts, multiclienting, and optimization. I'm looking to create the most efficient path to reaching my end game goal of late game bossing on a NL (I think I would need 20k+ HP minimum for this?)

I also plan to create other characters for fun. I don't want to invest too heavily in them, but don't want to 'ruin' their end game viability by not washing. Perhaps it would be better to play them normally, do HP challenges and then decide if I want to remake those chars?

I have done a fair bit of research and read guides, but many were a few years old and metas might have changed. How would you start over in the most efficient way possible? I am starting from nothing: no vote NX, no mesos. I would also like to document the "meta" journey to end game.

Questions:

• I heard "multimaging" is good to farm mesos? How many mages would I want, and when can they start farming? Can I farm on these without 'ruining' them for end game?
• I read that I would need a lot of stockpiled NX/funding for washing. It seems like I cannot wash my potential alt attackers right away, so would it be best to just focus on farming until I have NX? I intend on self leaching once my bishop is leveled.

TL;DR
Starting from zero, what is the most efficient path to end game bossing using multiclients and with no stockpiled NX?

Thank you for helping me nerd out in this old mushroom game