Loc: South Jersey (Pinelands)
In my experience it is almost always the tiny, tiny, tiny ones, that are problematic. There are years down here in SJ where you can't go outside without getting ticks on you. And most years there are weeks where I don't expect to go for a trail run without find a few – and that's staying on the trail.
Wander into bushes or high grass and you might find a couple dozen. I've complained of symptoms for years after I was treated - even with IV Ceftriaxone. I got prophylactic treatment many times after that.. These days my (very well known) infectious diseases doc says the tests are accurate and will not prescribe them. Whaterver, after an initial period, they always made me feel much better.