The cooling sleeves are relatively comfortable although quite tight, and I opted for medium and am of a slim build, definitely go a size or two up from what you might think.
Length is good, not sure if going up a couple of sizes affects that.
Whilst the top portion is a little tight the fabric is stretchy and blocks the sun well, I give them five stars because I was quite amazed at how well they do at actually keeping my arms cool when they're in direct sunlight.
I haven't done heavy excercise with them yet so can't talk of their functionality there. I bought them purely to protect from the sun when relatively still but out in the elements. I definitely felt instantly cooler when I put them on though whilst the sun was beaming down on my exposed arms.