You have plenty of time for squash to mature in your area. Most yellow squash take around 60 days from seed to harvest.

Definitely seeds.

There's time, but in the past when I've planted this late they've gotten destroyed by bugs. So you'll have to watch them carefully.

There's plenty of time for both summer and winter squash. I have had luck in the past with covering the plants with floating row cover until they start blooming. That way, the moths don't get to lay their eggs until then. You'll get several nice harvests before the doggone things do the plants in. I like to plant them in a new spot in the hopes that this will confuse the critters. This time of year, the plants grow very quickly. I have had summer squash bearing in 45 days. There is time, too, for winter squash. If you hurry, you might have pumpkins for Halloween. Just in case you don't know it, squash varieties that are curcubita moschata do not fall prey to SVB. I am growing only those this year and it is a joy to see the beautiful plants that have been in the ground and growing since April.

I just replanted zucchini due to squash vine borers killing my first batch. With good warmth, it takes around 30 days from seed to first harvest, so there is plenty of time. Mind you, I'm in zone 4, so you, in zone 8, have more then enough time.

Joe