If you have a Hexblade with Pact of the Blade (Pact Boon), the Improved Pact Weapon (Eldritch Invocations), and Polearm Master (Feat), with a Spear as your Hex and Pact weapon, then the modfiers to hit and for dmg should be the same when you attack normally and when you use the Polearm Master Bonus Attack and Polearm Master Opportunity Attack, but on my character sheet on DnD Beyond the bonus and opportunity attack do not seem to account for hexblades, as you can see in my screenshot below.

I am fairly certain that is a bug, after running it by a couple of people who are more experienced with DnD that I am.

The attacks generated by the Polearm Master feat are entirely generated by the feat itself and draw absolutely no information whatsoever from the weapon, nor from any other feats or class features. The system is pretty to look at, but not actually smart enough to put everything together to make it work correctly without the player manually customizing a few things on the character sheet.