types of yeast - whats the difference

Fresh yeast tends to start off fermentation a little faster than either dry type. I prefer it when i can find it. But it is also more perishable and therefore has a short shelf life. Instant dry yeast is essentially a higher potency concentration of active dry yeast. I suspect the standard dry yeast in Europe is the instant dry type, but it would be good to confirm that. And instant dry yeast doesn't require the soaking/proofing stage that active dry suggests. You can pitch instant dry yeast directly in with the flour and salt without pre-wetting it. Because instant dry yeast is higher potency, it can be substituted for active dry yeast at about 75% the quantity. The retail fresh yeast cakes sold in the US are hard to find, but tend to be scaled at 17g, which is roughly equivalent to 2.25tsp (or 7g) of instant dry yeast and equivalent to 3tsp active dry yeast. If I remember correctly, European fresh yeast blocks are sold in 25g packets, so a little conversion math is necessary. Fresh yeast should generally be crumbled and added to the liquid component of a dough before mixing in the dry components. When I can get it, I prefer fresh yeast for sweet, enriched breads like brioche and challah. I hope this helps. Bake on!

Use whatever you like and can get.
But for an American recipe that uses instant yeast (mixed in with the dried ingredients, no proofing needed), you'll need to modify the procedure a little.
Proof the yeast first, using a small amount of liquid already in the recipe, then add proofed yeast to other ingredients abs mix, then knead.