yeah doing both same time isnt a bad idea

you can actualy have less running that way

find any 3 nodes, of either of them, and you can run between the 3, wether it be 2 botony 1 mining or the opposite
youll progress well in both that way

as for quarry, same as harvest for botony, yes they serve purposes, items, alot of the items from them you cant get anywhere else

and when you hit grade 5 especialy youll want what items can drop from it