I'm sorry, I'm a little late to this thread, but maybe my input might help someone. This is my own experience/opinion with early apples in south/central Ontario Canada (Canada zone 5a, which I believe is the same as zone 4b USDA):
I have a four year old Williams Pride on B118 and it’s already producing as many early apples as my family can use. In a few more years, I’m sure I’ll be swimming in Williams Pride apples but that’s OK (for me) because I raise geese. The early apple varieties start producing around the time that grass slows down in midsummer. Early apples make up for the pasture shortage, so a B118 Williams works for me. But it might (or might not) be too much for you, eventually.
I grow Vista Bella, Sweet Bough, Pristine, Duchess, Williams, Jeffries (spelling?) & Golden Sweet, for early apples. They ripen in that order with some overlap & a bit of variation. (I don’t grow Yellow Transparent & Lodi anymore.) Out of this whole bunch, Vista Bella & Williams are probably the only ones I actually “need” to grow because Vista Bella & Williams cover the early apple season with (true) dual purpose apples. (I don’t consider YT a true dual purpose & Pristine, although imo it is a true dual purpose apple, it doesn’t start until Vista Bella finishes.)
Vista Bella seems to be getting rare & I don’t hear people talking about it much, anymore, which is a shame. It’s susceptibile to scab, but it’s still a “must have” apple (for me) because it’s still my earliest “good” apple. It ripens with or within a few days of Yellow transparent but it’s already sweeter & less tart than YT, even before it’s fully ripe. Also, even though it’s a relatively soft apple, Vista Bella’s slices actually stay intact in apple pie, unlike Yellow Transparent,which turns into fluff.
For anyone has the right conditions for Vista Bella, I highly recommend growing at least a branch of it. Mine gets scab, but as long as the leaves & fruit get raked up (or eaten by geese, in my case) there’s always enough clean apples for a couple of weeks of extra-early munching and an excellent,very early pie.
(I stopped growing Yellow Transparent & Lodi because they got killed by repeated, severe fireblight. Vista Bella has had the occasional strike but it has never lost an entire crop or an entire tree to fireblight or any other disease.)