Whats the difference between "-ist" and "-er"

The suffixes -ist, and -er are added to a base word to name a person who does an action: pitch, pitcher.

Some more examples:

carpenter      artist
painter        nationalist
banker         dentist

These all seem to be professions, but is there a conceptual difference between names ending with "-ist" and those ending with "-er"? Any history behind it?

From Wiktionary :

-ist

Added to words to form nouns denoting:

a person with a particular creative or academic role;

one who subscribes to a particular theological doctrine or religious denomination;

one who owns or manages something;

And :

-er

(added to verbs) Person or thing that does an action indicated by the root verb; used to form an agent noun.

(added to a noun denoting an occupation) Person whose occupation is (the noun).

The etymology part says that :

• -ist comes from Latin -ista from Ancient Greek -ιστής (-istḗs), from -ισ (-is) + agent suffix -τής (-tḗs)...

  • one who practises or believes.

• -er comes from Middle English -er, -ere, from Old English -ere (agent suffix), from Proto-Germanic *-ārijaz (agent suffix). Usually thought to have been borrowed from Latin -ārius from Proto-Indo-European relational adjectival suffix *yo- (“belonging to”)...

  • Used to form adjectives from nouns or numerals.

  • (masculine only) -er; Used to form nouns denoting an agent of use, such as a dealer or artisan, from other nouns.