I wonder if there is any Polish language proficiency requirement at all for the temporary residence permit?
No, there isn't.
Which visa do I use to enter Poland - either the standard 3 month visa or a 1 year National visa.
As a UK citizen, even now, post-Brexit, you don't actually need a visa to enter Poland for a stay of up to 90 days so there's no point in applying for a three month visa. I wouldn't bother with the visa at all. If you make your application asap after arrival you should be fine and if your overrun the three months during the processing period they won't deport you :)