Here is a link to a thread where I asked about long wall speaker placement.
Speaker Placement in Narrow Room
I ended up placing speakers against short wall, but my room is wider. I think that you could make a good case for listening in near field with speakers on long wall. What happens to your sound when your speakers are placed close to the rear wall? Placing them on the long wall will require that they are close to the wall. Placing them on the short wall will probably present room treatment challenges.
If you need 220 then yes, run a 220. I know that many power amplifiers can take advantage of the 220, but you are pretty much stuck listening in near field and I can’t imagine needing more than 120V 20Amp. I don’t know what the PS Audio power products are like, but if you are willing to put big money into power conditioners then you should be able to get the large current draws on peaks through an isolated channel on the conditioner. Look at the specs on the Shunyata Everest, or the equivalent product from Audioquest. The point here is that if you run 220, you will probably be looking at conditioners for 220 and 120v. I know that many here will tell you to plug power amps directly into the wall, but for me, using the Everest was a big plus.
Room treatment is something that requires watching lots of video and reading many threads. There isn’t going to be a definitive answer. People usually treat area behind speakers and first reflection. Don’t forget flooring, listening furniture and ceiling. Absorbing behind your listening chair will likely be necessary and challenging, with speakers on long wall.
If at all possible, make the dedicated room wider.
BTW.. Love the Holo May KTE and Aurender products.