The trick to removing the drain plug before it gets mangled.....Use a shallow high quality chrome 1/2" drive 15mm socket along with a 1/2" drive impact, Preferably a "Big Hammer" air powered one. Push up on the impact & give it short burst to rattle the plug loose, Trying to not let the socket cam off the head!
I have a roughly 95% success rate with the above.....If the plug is already damaged.....Weld a nut to it & zip it out with an impact. An OE oil drain plug for the same vehicle works as a replacement & won't round off again.
Exhaust Studs......(I do not live where they use salt on the roads)
*Spray them with a good amount of PB Blaster a couple times. Let sit for a few minutes.
*Wipe off the PB from the exposed threads & apply some Anti Seize.
*Use a 1/2" drive impact, A "long enough" Extension, And preferably a 1/2" drive Semi Deep 15mm impact wobble socket to hammer them off.
Using an Impact is the key.....Trying to remove the exhaust stud nuts with hand tools is almost a guaranteed way for the nut to gall on the stud or snap the stud off.
Use Anti Seize upon reassembly.