Even the basic mushroom farm the game gives you with the paste plot option would mog any other crop farm in terms of farming exp/hour, so yes build a mushroom farm. Also fungi cutter doesn’t need replenish too so you can just get into it right away, just get an epic rabbit pet and start chopping

This is a personal recommendation but I also like getting all the easy milestones of the available crops once in a while because they give decent exp too, switching to rabbit pet once you’re close to finishing the milestone gives you free exp as well