Re: Upholstery foam..
When we did ours the woman doing the cushions gave us a choice of soft-medium-firm-extra firm. She recommended firm for the berth cushions and firm for the salon cushions. She was right on the money.
As for the memory foam toppers some love them, I find them hotter to sleep on and less comfortable YMMV.
95 Catalina 30 Island Time
“Only two sailors, in my experience, never ran aground. One never left port and the other was an atrocious liar" - Don Bamford