Good question - I would ask his doctor but once they are getting close to two I would think they are less at risk for SIDS - and they do have children's pillows at Toys R Us I think, but probably the trick is to find one that is flat and not to big for their little neck. I babysat for an 18 month old and she already had tons of stuff in her crib, pillows, blankets, stuffed animals, etc. so I would think he is probably ready.
I moved my son to a toddler bed around age 2 when we were expecting his brother, and he loved it. I actually felt more secure that I did not need to worry about him falling out of the crib, since it is low to the ground (now that my boys are older, I have to worry about them falling off the top bunk lol). If you are a light sleeper and check on your child often you could move to the toddler bed soon - I would probably put up the toddler bed and leave it in his room (if there is room and if you use another mattress) for a while to give him time to transition. Maybe let him nap in it first to see how he does. The key is, "Whatever works" and if the change seems to disrupt his sleep, I would wait. If he is sleeping well in his crib and not trying to climb out, I would probably wait - don't try to fix what isn't broken.
You CAN use a twin bed with rails instead of a toddler bed, but it made me more nervous about him falling off - the advantage to a toddler bed is is uses the same mattress as the crib (if you want to save money). I like the ones that look like cars that are pretty much enclosed, but we used a wood one that looked like a real bed. There are lots of options.
Good luck!