Philip Klöcking has done a good job covering what the person being choked experiences. I will try to cover other considerations.
In my experience, feeling pain is largely separated from whether a choke successfully cuts off blood flow. Pain will usually cause people to tap even when the blood choke is not that effective. You can also choke such that the choke is not painful and does not impair breathing but is very effective in cutting off blood.
Resistance time varies widely. This depends on the person doing the choking, the person being choked, and more.
If a choke is not tight and continuous, it's often possible to resist for > 30 seconds. Any time the person being choked can temporarily relieve pressure increases resistance time. In competitive judo, the match will be stopped and the referee will stand the competitors back up fairly quickly. For poor referees, this can be before the choke has sufficient time to work.
When a choke is done very skillfully, you may not even have a chance to recognize the danger and tap before you pass out. This can be true both of rolling chokes where the pressure increases suddenly, and of the painless variety of choke.
I think time to pass out also depends on the physical state of the person being choked. I would hypothesize that competitors in match conditions with high heart and breathing rates pass out faster than people at rest.
While someone is being choked effectively, I usually see the following, in order:
- blood vessels in the head begin to bulge
- face color begins to darken
- eyes become glassy
After someone passes out, they may shake, sputter, urinate, or simply go limp. In the dozen or so cases I have seen, I would not say there is a normal set of things that happen or order that they occur in. This makes it difficult to tell when someone has passed out. When practicing chokes, I highly recommend having a third party present because they can often recognize someone has passed out before the choker.