Personally I did not need to put anything into energy for Koumei besides Equilibrium and Synth Deconstruct.
I am very much a “use the right tool for the right job” type player, and your Warframes are tools just as much as your weapons are. Of course you mix the fun in there, but the point is to not make a Warframe into something they’re not and expect efficiency and effectiveness.
As someone in this post already said, Koumei is a probability/statistics frame at her core. She has a ramp up period with each mission, and so in order to almost guarantee effectiveness, the biggest resource you have is time. In other words, she is not going to be effective in short missions. The other big resource you have is your arsenal i.e. the tools you can control going in. The trick is to maximize that by using tools and mods that will mostly give you stats that you know will not be provided by decrees.
So most notably that means not focusing too much on ability strength and efficiency in your arsenal, and instead focusing on interactions that can proc off of the decree effects, or flat modifiers for stats that won’t be touched by decrees such as range and duration.
And the last thing is to accept that your run might suck for the first 30 or so minutes. By around 30-40 minutes, based on probability, your run should start to settle in and you’ll see the pay-off of the decrees.
I have not personally subsumed any abilities yet, but the candidates would be her 3 primarily, and potentially also her 1. Omamori isn’t very useful in its current state considering it doesn’t actually prevent you from dying, and more or less is worthless beyond the small window between not needing damage mitigation and being prone to one-shot damage. Kumihimo is also fairly redundant in the context of her 4, and can be removed if you have no real need for diet Bunraku.
I want to come try it too lol, been waiting since day 1.