Hydropothecary announces expansion plans to increase production capacity to 108,000 kilograms per year of dried cannabis
4 gb of ram is so much. 8 GB is definitely overkill unless you are planning on doing something involving video. With ableton you would actually be fine with 1 or 2 gb, 4 gb is plenty.
For what you would spend on the RAM upgrade on the 21.5 model, might as well get the 27 and see if the 8GB is enough and add more later as needed. Unless you are working on mega-layered Ai or Ps files or editing video, you should be fine.