I tend to eat first these days, I didn’t have any breakfast for years but I did notice that a big hit of caffeine on an empty stomach (before lunch) could make me very jittery/spaced out.
Never can recall having a laxative effect from coffee alone, @drdre89 is your early morning coffee dairy free? (low fat milk, however, certainly has that effect on me).
All coffee is a round 5 point something pH - acid content of all coffee is similar, but it varies in flavour perception (tritatable acids). The flavour in coffee is heavily reliant on acids (including perceived sweetness & bitterness), along with soluble fibre, they’re supposed to do you good, if anything.