There are no IR class ratings in FAA land, only categories. However, if you take your IR checkride in a SE airplane and later add a ME rating, your certificate will have the ME with a VFR only restriction unless you "demonstrate instrument proficiency" during the ME checkride. Normally a FAA certificate just says INSTRUMENT AIRPLAINE or INSTRUMENT ROTORCRAFT.
There are two IR writtens for airplanes. The "normal" IR written and a "foreign pilot" written. You want to take the normal written so that the rating will move to your commercial certificate when you take the checkride. The "foreign pilot" written only adds the IR to your 'based on" certificate. Both happen without a checkride.