I would argue the “professional” fitting. There is only one seat and block position… it either works for you or doesn’t. There is only different seat sizes.
The only “fitting” is the shape of the under panel for the horse.
No one should be sitting up against the cantle, the fact that someone was way back off the block and against the cantle in a “chair seat” says super tight hip flexors or tight low back… probably both.
I can ride in the size one… super tiny, the size two which is snug and the perfect for me, the size three. But I am loose thru my back and hip flexors and can stay quite centered to make it work for the clients with ponies.
If the seat design works for you, you should not feel the blocks or cantle unless you are posting or pulled forward.
For me the block is not there AT ALL unless I need it while sitting. Actually feels like a super close contact with no blocks… well until I need them.