I'm finishing a room that will have new carpet installed. I plan to install the baseboard height about 1/2" off the slab so carpet can flow underneath. The room is all painted (trim/walls), but no base is installed. My question is: should I cut the closet/doors trim/jambs at 1/2" as well (before base install) so the carpet can flow under or is it not a big deal? The carpet will be about 5/8" thick and 1/2" pad, uncompressed.
I always hold casing to the same height as the base trim (3/8" or 7/16" is enough--1/2" risks showing a gap with thinner carpets). However, if the casing is already installed, don't bother making cuts now. Carpet layers can easily deal with that situation by tucking against it. It shouldn't be a visual concern.
Casing and base should both be at he same level. From the picture there are a couple of ways to cut it if you want to cut it (I'm not sure it's necessary, the carpet should hide the difference). You can get a trim saw that is designed to cut casings for floor installation, should be able to rent, it's probably too expensive to buy for just one job. If it were me, I'd carefully cut it with one of the Japanese back cut saws. The make really clean cuts and are very easy to use.