You're right that boczek has more flavour, esp. the home-made version if you can find it (super difficult, imo). Usually the home-made boczek will be meatier/more smoky/more garlicky than, the store bought-stuff.
Słonina has little flavour, besides slight smokiness + saltiness. Normally it's used to highlight the flavour of the next dish or as a snack served with vodka. Similarly to lard, you'd serve it before the main dish to make the palate more sensitive towards any fat-soluble flavours. I'd say słonina is 90-95% fat plus a barely noticeable amount of meat.
The Siberian one I got though... had waaaaay more garlic and a little bit of pepper. It was lovely, but something I'd eat at the "caviar serving" amounts.
Useless trivia #123: it's likely a coincidence but in Polish "słonina" literally means "elefant meat" ("słoń" /swoń/, comp. the suffix -ina w. "wołowina" for beef, "wieprzowina" for pork).
> Maybe I need to work on my tofu this year
Smoked tofu is sooo good. I have some good kimchi + gochujang I want to cook tonight with pork belly, but now you made me think of replacing the meat with some smoked tofu I bought.
