What figures of "Total impressions" and/or "Average position" are considered good at Google Search Console Performance?

This is so subjective to your industry, what keywords your site is ranking for, and the search volumes for those keywords.

Rather than focus on what is 'good', I would focus on charting improvement. Is your site improving in search performance? What can you do in order to spur on more growth?

Use search console as a record of your progress rather than a benchmark to compare yourself to your competition.