if this is an edge you'll trip on you have more problems than just the baseboard being out of whack....was it level before?

Yes, it was more level before. The bathroom and master bedroom are all on the same concrete slab base. when they installed the radiant floor heat and tiles, there was significant thinset and self leveling cement added...

Yes, some radiant products have a minimum of 1/2" mortar needed for the wiring. You could cut down the baseboard in the bathroom to keep the same height for bath and bedroom or angle cut the baseboard leading into the bedroom and paint the raw edges. The angled cut would also signify a reminder that there is a slight step up.

Also, your baseboard shouldn't be sitting atop of the tack strip. Tack strip will need to be pulled out a little more for best grabbing of carpet to tuck along baseboard.

You can do what GDS LLC said or you can also do something like this and you make a miter on the reducer letting die into the edge of moulding, or extend the bottom of the base and let it die into reducer.

I don't know why that floor was raised so high, it should have been much lower, this is why using Ditra for underlayment makes such a big difference, its only 1/8" thick and it makes a structural floor, with tile you right @ 3/4".

Hi all! Thanks to everyone for the great comments. It was really appreciated. The carpet guy was able to "build up" the area in front of the dropoff with a little extra tack strip and folding so the bath runs smoothly into the carpet, and we could install the floorboards slightly higher all around the room. I'm happy with the outcomes, and super happy with the support from the Houzz community. Makes this whole remodel experience much less hectic.