The physical disc is PAL only and my TV is NTSC. I made a UK psn account and downloaded a free to play game to test it, and it did work, just not sure if it's the same story with physical games.

Not since before HD.

You should be ok, I don't think modern consoles are region locked, but don't have any first hand experience with physical games.

Technically PAL HD TV's are still supposed to run at 50hz while NTSC HD TV's run at 60, but I don't think any TV since the late 80s has actually had any trouble switching between 50 and 60hz modes, and I'd say most games run at 60 even though the console system would tend to adhere to the 50 or 60 hz preferences of the TV.