Never tried them before. Open up a bag a give them a good sniff, that should tell you if they will work well in the beer you are planning for them. For a new variety, I like to smell them and then smell a variety, like Cascade, that I am familiar with. It gives me a way to compare intensity and type of aroma.
When you are recirculating for the last 15 minutes or so you are really filling those small crevices up with hop pellet gunk. You should find another way to sanitize the plate chiller and then wait for the pellets to fall down to the bottom of the kettle. Pull clear wort off above the level of the pellet pile at the bottom and you shouldn't have any problems.