Is 鄇 used in modern Chinese?

No, this character is extremely rare and appears almost exclusively in historical texts referring to an ancient place name.

How is 鄇 different from 侯?

鄇 is a place name character with the town radical (阝), while 侯 means 'marquis' and is a much more common character.

Generally not recommended due to its obscurity. Most people would not recognize it, and it might cause practical difficulties.

鄇Tone 2

hóu ｜ 11 strokes ｜ radical:

Hóu — an ancient place name;

a historical settlement during the Spring and Autumn period in the state of Jin.

Hóu — an ancient place namea historical settlement during the Spring and Autumn

Ancient settlement HóuHóu in the state of JinHistorical place name Hóu

Hóu was a settlement in ancient Jin (鄇 was a settlement in the state of Jin).
The location of Hóu is mentioned in historical texts (鄇 is found in ancient records).
This character appears primarily in classical Chinese contexts (鄇 appears in classical texts).

Hóu was a settlement during the Spring and Autumn period, located within the territory of the state of Jin.
The character is extremely rare in modern usage and appears almost exclusively in historical or classical texts.