Thank you @Butters and @Nozbat. I think I'm going to buy the Clockwork & Chivalry book. Though I'm not sure if the setting of Clockwork & Chivalry will be to my liking, I find it a nice extra for almost the same price as the rulesystem only Renaissance Deluxe. Even if I won't use it in my games (or not as is written) it will be a nice showcase of how the rules can be used with a Renaissance era setting and I can mine it for ideas for creating my own setting. I guess that having the extra setting material in it won't make it much harder or fiddlier to use it as a rulebook either.
Also, thank you for sharing your experience with the different POD versions. I also find it that books with glue binding last longer in softcover format so I will go with that. And it's also cheaper which means that I can buy more from the same budget.
About Renaissance: 1520 I read a great review here on the forums by @StevenGEmsley so it's definitely on my list of books to buy in the future. By Mythic Russia you mean this book @Nozbat? It's also available in PDF as well if anyone's interested. And if you have any other historical (or mythical) source material recommendations, please let me know. I know it's a Renaissance forum but I'm also interested in early medieval and ancient history sources as well.