Likely to be quiet or full of tourists? Do they have Grab or Bolt there?

It's quiet now, it will be dead in June.

 

Yes, they also have the Cambodian equivalent called Pass app.

 

It also has Grab food, Grab tuk tuk, Grab car, Grab bike, etc

Depends on the weather. Although currently the monsoon season, there have been several dry days with sunshine. On Friday 6th June, I took a drive in the glorious sunshine with my usual tuk-tuk driver to enjoy viewing the temples in the Angkor Wat Archaeological Park (I have a free pass). It was very busy with many tourists and other visitors. By coincidence my usual tuk-tuk is a GRAB one.