Shadow spawns (more specifically common pokémons)

Hello,

First of all, I don't want to sound like I'm complaining. I'm mostly just being curious, and since it's something that is quite time-consuming, it is important to me.

From October to January it felt like there was a reasonable amount of shadow mons (mostly slowpokes obviously), I would say 1 a week in average, which is completely fine and not really what I am going to talk about. However, during the last 2 months, it feels like there was dramatic decrease in terms of shadow spawns, especially for common pokémon (yeah, Slowpoke, we're talking about you, but also about Taillow and, in a way, Budew as well). So the first question I'm asking is :

Was there a change of spawn chances for shadow pokémon, or are we just collectively avoiding shadow commons ? Note that rare spawns have not disappeared, I saw at least 1 Noibat, 1 Deino and 1 Houndour since January 1st - which is more than all shadow slowpokes I've heard about in the last 2 months and a half. Comparatively, this would mean at least 10 to 20 slowpokes, considering the relative rarity.

This brings my second question : how do spawns live together in a map that has more than 2 pokémon counterparts potentially spawning in the same area ? I know that in Pinkan, only pink and shiny mons can spawn, and that in nesting grounds, shiny and event mons can spawn, but is it possible for a shadowpokes to spawn during an event when it already has a form ? In that case, does that mean shadowpokes are less likely to spawn, or just that normal slowpokes are slightly less likely to spawn ? And, last question, do the Crux of Melody bosses (Taillow, Swablu, Larvesta and Budew) have shadow counterparts ? I was expecting to see at least 1 of them in global encounters after 2 weeks of intense farming.

Thank you for taking time to read this all, and thank you in advance for responding.