Spring is truly a beautiful time in the Netherlands. Coming from Florida, it's cold to us, but it's worth it. You didn't specify what kinds of flowers, just that it doesn't have to be tulips. But you can't miss the tulips, truly, you shouldn't! Here are a few links to help answer some of your questions.
Keukenhof Gardens, to my way of thinking the goddess of spring bulbs (and more): https://keukenhof.nl/en/
From Tulips in Holland (it's last year's, but it still applies):
We didn't see the parade, but the floats are parked in Haarlem afterwords, an incredibly fragrant street party:
In Rotterdam there is a lovely botanic garden/arboretum with all sorts of blooming things. This spring we ate our picnic lunch in the arbor surrounded by lily of the valley in full bloom. It was hurtful, yes just hurtful.
All around you will find blooming things, crab apples, Kwanzan cherries, wisteria climbing up multi-story buildings, window boxes filled to bursting with spring celebrations. This is truly a country that knows how to celebrate spring.