In my opinion 6 inches is ideal. Above that and it probably would hurt to get a blowjob and what's the fun in that
No bro it depends on the girl. Some freaks shove your dick down their throats like nothing lol. Now of course, a smaller girth will allow for the female to provide a better oral job. I personally dont feel anything from BJ's. Perhaps due to my girth? dont know, but I dont mind them.