I've been using Tibhar Hybrid rubbers since 2018. Used K1 Pro for about a year, then switched to K2, a year ago tried K3 for one practice session, and about a week ago switched to K2 Pro. Never used K1 Euro version.
You'll probably find detailed answers you're looking for in the above links but here is a very quick TLDR:
K1 Pro - less tacky than H3N, largeish pores, factory boosted, etc
K2 - closest to H3N, properly tacky, fine-pored hard sponge, etc
K2 Pro - less tacky than K2, more tacky than K3, fine-pored hard sponge, faster than K2 but nor as fast as K3.
K3 - very little tack, largeish pored sponge, very fast compared to H2N or K2