Can I make a P-trap for 2 inch PVC out of a 90° and 2 45° elbows? The 2 45° elbows would be arranged in an
I'd be very careful with that line of thinking. The combination of a short and long leg in a drain creates a siphon. In the case of your photo, if the section heading off left makes a short turn downwards gravity may empty the trap during heavy use leaving you with a wonderful open connection to the sewer.
While cleanout isn't the major issue, it is a consideration too. At least in a trap without a cleanout you know where children's toys and wedding rings are. That setup looks like it would happily pass hairballs, grease, and anything else further down the pipe. Not only will blockages be tougher to clear when they're far away, they'll also stop multiple drains from working. There's nothing quite like a sink that causes the toilet and washing machine to overflow.