Hi @bpcleary,
Hole size and spacing are two (what I call) personal factors with some people seeming to be able to play pretty much any harp regardless of those two and others more comfortable with, say, larger holes or closer spacing.
I am sure you will eventually find yourself in one or the other of these “factions” of players.
For some harp models it is possible to buy custom combs that are made for that model’s reed plates and these combs can give you somewhat different hole sizes and/or spacings.
Regards,
– Slim