Temperature on both will give you a ballpark idea of doneness but probing for a butter like feel is when it’s done. Some brisket may probe tender around 200 then other cooks with different briskets may not probe tender until 210, so if those briskets are pulled in the 200-205 range they could seem dry. Pork butts are much easier and way more forgiving.
If I’m going to reheat for an event, I always finish the cook in a foil pan so I can catch all the rendered juices. Remove the brisket from the pan when done to rest and cool the pan so you can de-fat the juices. Leave the brisket whole and place back into the pan and foil cover to refrigerate. Reheat in a roaster whole with some juice 225 for a couple hours then turn down to about 150 to hold. Slice brisket before serving and place back in the roaster. The liquid from 1 packer brisket is generally enough warming liquid for 2-3 briskets.
For pork the process is same except I will pull the pork after cooking but pull it into larger chunks, this helps it both cool down faster and heat up faster later, make sure the cooking juices are with the pork when warming. Finish shredding the pork before serving, again holding at 150 for serving.